Rev hang - a curse or blessing

About 7 years ago car owners, including Honda fans, started noticing that revs tended to drop very slowly when upshifting gears, making smooth gear changes painfully slow. Numerous comments appeared on various Forums devoted to different makes and models of cars with manual transmissions. Some were critical, others indifferent and few even praised this "feature" for supposedly making gear shifting and "rev matching " easier.

Range of possible explanations were offered, most commonly asserting that rev hang was somehow meant to get rid of unburnt fuel from intake manifold or cylinders. Some argued that heavy flywheel was to blame, while others insisted the rev hang was intentional to make rev matching easier for people not used to driving stick.

I spent the last 2 years examining the rev hang and experimenting with possible ways of its removal from different car models. I came to the conclusion that its introduction was indeed intentional and inevitable but not for the purpose of assisting the driver. It came about because of the need to meet the ever-tightening exhaust emission standards imposed on car manufacturers by Government clean-air agencies all over the world. I explained the intricacies of rev hang, including videos and charts in my Website devoted to the rev hang.

Car owners minding, disliking or even hating rev hang and wishing to fix their cars are being offered various "tunes" predominantly designed to increase power and improve throttle response, torque delivery/spread, drivability and provide other advertised benefits. Judging by Web responses some tuners were completely successful in eliminating the rev hang whilst others were able to reduce it somewhat. The apparent downside of "tunes" involves, aside from the cost, question marks about their impact on continued warranty of new cars modified in such a way. Regardless of what people may say, the fact remains that current OBD (on-board-diagnostics) protocols include provision for car manufacturers to detect when ECU was last flashed. It remains to be seen if and how they decide to use this facility in assessment of claims for a major engine failure, if it were to happen.

There are car owners not seeking power increases and hence not interested in "tunes", who are still annoyed by the rev hang in their cars. They have by now become almost resigned to the situation that "rev hang is a common feature in modern cars". This seems to be the prevailing attitude, judging by the diminishing number of complaints about the rev hang found online in past 2 years or so. As young people buy newer cars, they become accepting of the new way they drive, perhaps because they never experienced the delights of changing gears in a car not afflicted by the rev hang. Drivers are forced to adjust their driving style to suit their cars. I turned 60 and can say that it was never like that before. Until recently car manufacturers built cars to accommodate the needs and desires of their owners. The tables have turned, it seems.

I wonder what other Honda drivers think of the rev hang. If it bothers you, do you believe that market exists for a cheap stand-alone module designed to do nothing less and nothing more than completely remove rev hang from any car? Such module exists and is easily removable, unlocked and freely transferable between different cars.

It is quite the bother. I believe its a "feature" introduced from the DBW (drive by wire) throttle bodys. I had this same issue on my Polo GTI which was annoying. Especially with a lightened flywheel. I believe the only way would be to get a tune, as you have already mentioned. Unfortunately there is not much else you can really do with getting rid of the pain that is DBW

Rev hang is annoying but there for emissions sake as you say... I learned to drive with it, even then I could tell it was awful. Had to granny shift and couldn't double clutch like I should.

Have you considered one of these thingys? http://www.ozhonda.com/forum/showthr...tle-Controller

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Originally Posted by RenzokukenJ

... I believe its a "feature" introduced from the DBW (drive by wire) throttle bodys. ...

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The DBW throttle is not causing the rev hang, its introduction only made it easier to implement the rev hang. Even before DBW in mid-70's car designers made the carburetor butterfly close slowly by adding a vacuum operated dash pots.
The pain is not in the DBW throttle system, it is in the ECU program instructions using the DBW to perform unnatural acts, like the rev hang.

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....... Unfortunately there is not much else you can really do with getting rid of the pain that is DBW

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I wonder why you said that when I wrote yesterday that an electronic module has been invented that kills the throttle hang. I have one in my '12 Accord Euro and it works a charm (demo is in this YouTube video).

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Originally Posted by curtis265

…….Have you considered one of these thingys? http://www.ozhonda.com/forum/showthr...tle-Controller

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Yes, I bought one in January 2014 and thoroughly tested it when connected to a throttle pedal in test rig. Its function is to change the relationship between the position of throttle pedal and the sensor voltage. It simply creates additional maps (9 for power and 7 for economy modes) and these have no influence on rev hang in any conceivable way. The device just makes the driver feel that his car is performing better and this is essentially true in the sense that the engine revs higher for any given throttle pedal input when in power mode against the standard setting. Attachment 28594Attachment 28596

Oh, I was under the impression rev hang was a function of the pedal input.

a signal amplifier is a bit lame..

well, you can always use the haltech elite system :))

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Originally Posted by aquasurf

The DBW throttle is not causing the rev hang, its introduction only made it easier to implement the rev hang. Even before DBW in mid-70's car designers made the carburetor butterfly close slowly by adding a vacuum operated dash pots.
The pain is not in the DBW throttle system, it is in the ECU program instructions using the DBW to perform unnatural acts, like the rev hang.


I wonder why you said that when I wrote yesterday that an electronic module has been invented that kills the throttle hang. I have one in my '12 Accord Euro and it works a charm (demo is in this YouTube video).


Yes, I bought one in January 2014 and thoroughly tested it when connected to a throttle pedal in test rig. Its function is to change the relationship between the position of throttle pedal and the sensor voltage. It simply creates additional maps (9 for power and 7 for economy modes) and these have no influence on rev hang in any conceivable way. The device just makes the driver feel that his car is performing better and this is essentially true in the sense that the engine revs higher for any given throttle pedal input when in power mode against the standard setting. Attachment 28594Attachment 28596

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Out of curiosity what cars did they introduce that with?

And yeah, I forgot about that module lol.

Its a Curse of DBW in my opinion.

It happens in my STi, if your shifting gears like race car on Intelligent Mode.

Im just curious on your reasoning behind it being an emissions thing?

Unburnt fuel gets sorted by PVC System. Plumbed back into the intake track for a second shot at redemption.

This is my 1st DBW Car and its the only car that I've owned does this.

I also know its cos Im shifting like race car when it happens.

If just driven Civil, granny shifting in traffic is all good.

I also don't think its an emissions thing. On S & S# there is no hang in my car, behaves like a cable operated throttle & more sensitive pedal & more power.

Little bit better then module as on I - limited to 60% throttle at max pedal depression. IE throttle plate wont open past 60% even when given the full blow.

I also don't see how it would help upshift don't you want the rev's to drop when upshifting instead of hanging around?

Its the downshift where the effect would be sort of desirable to newer drivers.

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Originally Posted by RenzokukenJ

Out of curiosity what cars did they introduce that with? ....

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I do not know when rev hang first appeared. My first experience was in February 2003 in Spain where I hired a new Fiat (I think it was a Punto model) and in 7 days I drove it I could not figure out why I could not change gears smoothly.

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Originally Posted by amant02

…Im just curious on your reasoning behind it being an emissions thing?

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I am positive about that. The problem car designers try to solve by rev hang is the sudden leaning of mixture when throttle is closed abruptly as it generates a spike in NOx (oxides of nitrogen) emissions. I had car emission lab test results from about 1985 (the voluntary test costing me over $1000 at the time), proving that beyond doubt.

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… Unburnt fuel gets sorted by PVC System. Plumbed back into the intake track for a second shot at redemption.

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I agree the rev hang is not about removing unburnt gasses. In fact, it works to the opposite effect because it intentionally feeds additional fuel to the engine when throttle pedal is off. This causes the engine (and car) decelerate much slower that would otherwise be the case, bringing on all the nastiness of hanging revs.

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… This is my 1st DBW Car and its the only car that I've owned does this. I also know its cos Im shifting like race car when it happens. If just driven Civil, granny shifting in traffic is all good.

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People describe their experience with hanging revs in different situations. Some write about revs hanging at fairly low engine speeds, say 3000 rpm, others cannot get idle down to the normal 700-800 rpm without revs first hovering around 1500. My concern and solution deals with the problem of revving my engine high and the revs not dropping fast enough when upshifting. Generally, the rev hang gets worse with increasing revs. I can upshift at low rpm without difficulty but I did not buy my Honda VTEC to "shortshift" when I wish to use all of its 140 kW at 7000 rpm.

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… On S & S# there is no hang in my car, behaves like a cable operated throttle & more sensitive pedal & more power.

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I understand some cars, like yours, have several programs in their ECU and engine control can be varied by the push of a button.

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… Little bit better then module as on I - limited to 60% throttle at max pedal depression. IE throttle plate wont open past 60% even when given the full blow.

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I find it interesting that people often refer to the opening of the throttle plate as if it was the determining factor in setting engine revs. Would you believe that in EFI cars it is possible to have the throttle plate fully open (by the ECU, of course, taking cue from the DBW throttle pedal) and yet go nowhere? This happens when the ECU cuts signal to injectors, stopping supply of fuel to the engine.

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… I also don't see how it would help upshift don't you want the rev's to drop when upshifting instead of hanging around?

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Of course, I want the revs drop fast when upshifting. This was the reason behind my efforts to delete rev hang. If you want to read more about my rev hang investigations, look at my rev hang webpage.

I thought rev hang was to allow a smoother throttle cutoff, so that you don't dump unburned fuel into the ca, supposedly prolonging it's life.

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Unburnt fuel gets sorted by PVC System. Plumbed back into the intake track for a second shot at redemption.

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How do you suppose unburnt fuel goes into the PCV system? I think your motor may be on the way out if that's the case. Perhaps you mean EGR? Even still this does not loop 100% of the exhaust back into the intake, so this is why they introduce rev hang, to burn the last of it.

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Little bit better then module as on I - limited to 60% throttle at max pedal depression. IE throttle plate wont open past 60% even when given the full blow.

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How do you know that the power is not being controlled by the wastegate? or valve trickery?

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I also don't see how it would help upshift don't you want the rev's to drop when upshifting instead of hanging around?

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I would rather my revs drop to the right level rather than hang and sacrifice smoothness

I think that rev hang makes the car easier to drive for the average commuter. I've been driving modern cars for so long now I'd forgotten what it was like before.

I recently put my EK4 on the road and it has a good, old school cable throttle, and revs almost instantaneously return to idle when you lift off. It takes me a couple of gear changes to get used to it (in fact, the faster you shift, the smoother it is to drive - within reason of course). My L-plate son, on the other hand struggles with the immediate drop in revs, and it takes him much longer to get the hang of driving the Civic. Once he hops back into the Focus, he's immediately smoother on the controls. He's still at the stage where he takes his time shifting gears, and generally does everything fairly slowly when he's driving. This works with modern DBW systems, but isn't so smooth on old school un-assisted everything cars.

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Originally Posted by curtis265

I thought rev hang was to allow a smoother throttle cutoff, so that you don't dump unburned fuel into the cat, supposedly prolonging it's life….

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I am struggling to understand this supposed prevention of "dumping of unburnt fuel" as the reason for rev hang. Let's say we have an engine without rev hang to perform the stated function. Backing off the throttle shuts both the air (via throttle plate) and fuel (via injectors) immediately. My question is how do you explain this "dumping of unburnt fuel" immediately afterwards? It just does not make sense, especially as I know for sure (I have a lot of test data, videos etc.) that the rev hang in fact keeps feeding fuel to the engine after the throttle pedal was returned to idle position. If there was to be any problem with dumping of fuel, the rev hang would certainly make it worse and not better.

You are right that (small degree of) rev hang allows for smoother throttle cut off. With zero rev hang drivability of manual cars would suffer through drive-line snatch. This is the accumulation of clearances and small free-plays in the gearbox and differential that could otherwise be felt as an unpleasant harshness, jolt or thud/shock when engine power was suddenly applied or reduced.

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How do you suppose unburnt fuel goes into the PCV system? I think your motor may be on the way out if that's the case. Perhaps you mean EGR? Even still this does not loop 100% of the exhaust back into the intake, so this is why they introduce rev hang, to burn the last of it.

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This article should answer your question about the PCV. Based on my findings I would say that PCV and EGR recirculation systems have nothing to do with the rev hang.

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Originally Posted by Hondarally

I think that rev hang makes the car easier to drive for the average commuter. I've been driving modern cars for so long now I'd forgotten what it was like before....

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Exactly right. Thanks for confirming my opening words that as young people buy newer cars, they become accepting of the new way they drive, perhaps because they never experienced the delights of changing gears in a car not afflicted by the rev hang. My two daughters learnt to drive in a vintage 1991 carbureted Suzuki Swift with cable throttle and are now able to recognize the rev hang when they come across it in their newer cars. They do not mind it much, though, as they are usually in no hurry to change gears.

Theoretically speaking, would you not say that releasing the pedal suddenly will cut off ignition? So any fuel that hasn't finished the compression cycle will be dumped out the exhaust. It will ignite in the cat creating that crackling and popping we all know and love.

I do not know if a dbw equipped car has no popping.

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Originally Posted by aquasurf

I Would you believe that in EFI cars it is possible to have the throttle plate fully open (by the ECU, of course, taking cue from the DBW throttle pedal) and yet go nowhere? This happens when the ECU cuts signal to injectors, stopping supply of fuel to the engine. Of course, I want the revs drop fast when upshifting. This was the reason behind my efforts to delete rev hang. If you want to read more about my rev hang investigations, look at my rev hang webpage.

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Wouldn't that lean out the fuel? More air without increase in fuel?

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Originally Posted by curtis265

How do you suppose unburnt fuel goes into the PCV system? I think your motor may be on the way out if that's the case. Perhaps you mean EGR? Even still this does not loop 100% of the exhaust back into the intake, so this is why they introduce rev hang, to burn the last of it.

So using this logic curt, your engine must be on its way too. Wait wait 100% cars on the road, their engines must be on its way out, cos of unburnt fuel in the PVC System. All engines will make a little bit of unburnt fuel. Specially Factory tune turbo cars as they are tuned to run rich from factory.

How do you know that the power is not being controlled by the wastegate? or valve trickery?

I guess to some extent these are used as well, isn't the throttle basically a valve for air? so it is valve trickery. Since there are changes to amount of air intook by the engine so corresponding adjustments must be taking place in the wastegate, since there is less spool.

I would rather my revs drop to the right level rather than hang and sacrifice smoothness

This I agree with

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Originally Posted by amant02

Wouldn't that lean out the fuel? More air without increase in fuel?

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I do not think so. You can possibly lean out a fuel mixture, that is to change proportion of air and fuel in it, but if you have no fuel, then you do not have a mixture to lean out. You have just air and it ain't no pollutant.

Edit: Initially, the injected mixture would suddenly lean out as fuel supply was being shut off and emissions would spike. This is the very reason why car designers try to avoid it by adding the rev hang.

I’ve been contemplating replacing the ancient CB7 (24 years and 380,000km) with a somewhat newer Euro. I haven’t yet driven one, but am disheartened to discover that they seem to suffer the dreaded rev hang quite badly, possibly steering me toward a different car (Mazda 6 maybe, but that may be no better...?).

The CB7 (and probably many other Hondas of the era...?) also suffered excessively from rev hang ex factory, but since it predates FBW Honda ‘achieved’ it by means of the IACV (idle air control valve). On the overrun the ECU would momentarily hold the IACV open, creating the highly irritating 'rev hang'. I ‘fixed’ this by blanking off the ports in the IACV, simply by inserting a thin aluminium plate between the IACV body and plenum bodies. Of course this disabled the idle speed control function, so parasitic loads on the engine resulted in a lower idle speed (I had to increase base idle speed to 900rpm prevent excessive vibration at sub 500rpm with AC etc on).

Initially I tried simply disconnecting the loom from the IACV, which did stop the rev hang, but caused other issues. Of course it triggered an irritating CEL, but worse it seemed to cause the ECU to cut the ignition and / or the injection on the overun, which created unacceptably harsh off / on throttle behaviour. Simply blanking off the IACV ports didn’t do this (the ECU doesn’t ‘know’ that the IACV isn’t working, so doesn’t seem to cut overrun ignition and / or injection), only stopped the rev hang with no other issues (other than disabling idle speed control, which I could live with).

I agree this is all to do with reduction of Nox emissions , this was what I gleaned from my related research some years ago. Simply holding the IACV open (or with FBW cracking the throttle plate) won’t cause the rev hang on its own. For the rev hang to occur fuel needs to continue to be injected (and ignited) while the throttle plate or IACV allows air to pass into the plenum and cylinders. If only the unwanted air flow is permitted (with no fuel and / or ignition), then if anything the rpm would drop even faster, somewhat like an unrestricted diesel engine on the overrun.

This is because unignited air entering the cylinders will act to slow the engine, because cylinder compression is still occurring (less air = less compression, requiring less ‘work’, but more air = more compression etc). The effect is likely small as the compressed air will ‘give back’ some of its ‘stored’ energy to the crank past TDC, but when the air is initially compressed it will get hotter, so rotational energy is ‘lost’ as heat to the cooling system and down the exhaust, which in theory would manifest as a somewhat faster rev drop (with a partially open throttle or IACV allowing more air in, but no fuel burning).

I can’t see any easy way around this problem with a FBW system. Only some sort of piggy back device on the ECU, or reprogram some parameters of the ECU itself (possible with the Honda ECU??). Maybe I need an old (but nice, enough...) Integra or Prelude instead, something with an IACV system I can bypass...?

Regards,
John.

There's a much cheaper ecu reflash that gets rid of the worst of revhang

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….I can’t see any easy way around this problem with a FBW system....

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John, I agree with every word you wrote except the above. If you are in or get around to Sydney, I would love to offer you a test drive in my 2012 Accord Euro (CU2) 6-speed M/T I managed to cure of the rev hang completely and without ECU re-flash.

I encourage you not to give up on the late model Accord. When mended, it is a beautiful car to drive. I never had a Honda before and picked up my first one a month ago (mainly as a challenge to fix its rev hang) at auction for less than $16K with GPS and 50K km (also with hardly any thread on tyres and 2 days of rego left). I can imagine that previous owner got tired of the rev hang and decided to dispose of the car. His loss was my gain :).

I love the car and revving the VTEC to 7 grand for a snappy upchange. I made a minor mod to the traction control (or VSA - Vehicle Stability Assist) to disable it automatically on each take off and re-engage at 30 km/hr. to avoid the horrible bogging-down feeling at speedy take offs. The VSA was far too aggressive, cutting down power at first sign of traction problems, well before any wheel spin.

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Originally Posted by aquasurf

John, I agree with every word you wrote except the above. If you are in or get around to Sydney, I would love to offer you a test drive in my 2012 Accord Euro (CU2) 6-speed M/T I managed to cure of the rev hang completely and without ECU re-flash.

I encourage you not to give up on the late model Accord. When mended, it is a beautiful car to drive. I never had a Honda before and picked up my first one a month ago (mainly as a challenge to fix its rev hang) at auction for less than $16K with GPS and 50K km (also with hardly any thread on tyres and 2 days of rego left). I can imagine that previous owner got tired of the rev hang and decided to dispose of the car. His loss was my gain :).

I love the car and revving the VTEC to 7 grand for a snappy upchange. I made a minor mod to the traction control (or VSA - Vehicle Stability Assist) to disable it automatically on each take off and re-engage at 30 km/hr. to avoid the horrible bogging-down feeling at speedy take offs. The VSA was far too aggressive, cutting down power at first sign of traction problems, well before any wheel spin.

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How exactly did you fix the issue?

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Originally Posted by RenzokukenJ

How exactly did you fix the issue?

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My story of the rev hang fix is here.
The VSA fix was simpler but different.

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Originally Posted by aquasurf

My story of the rev hang fix is here.
The VSA fix was simpler but different.

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Thanks, I might look into it for the fn2...

Aquasurf,
Thanks for the kind offer. I’d take you up on it but it’s a long way to come from the Mid North Coast, and at the moment I have no other excuse to visit the Sydney rat race...

I’m fully in your camp re the horror of rev hanging, it really spoils the gear shifting experience. My old CB7 became a much nicer car after it had been eliminated (and the light flywheel, and my modified short throw shifter, and the Konis, and the stiffer springs, and the stiffer rear ARB, and deleting the front ARB, stiffer bushes, braces etc etc).

The VSA mod sounds interesting, but is it this that has addressed the rev hang issue? If so how? If not, then what did you do??

When I bite the bullet on a new car, it will be a much older ‘new’ car than yours. Older higher K Euros are only now starting to drift into the reach of my bank balance (besides, spend too much $ on a car and there’s less left over to feed the racing kart...). I’m starting to see what at least appear to be reasonable early MY Euros on the market for sub $6000, which would be around where I’ll be looking (when the time comes).

Experience with Hondas suggests higher ks aren’t necessarily a problem if the car has been looked after. I’d be happy with a mechanically sound car that might be a bit ratty on the outside (I live on a dirt road, and with a dirt road you shouldn’t get too worried about your cars being cosmetically pristine, that way lies madness...). At any rate, the CB7 is getting just a bit too tatty even for me, time to think about retiring her. Our other car is a Saab 9-5, which is nice but nowhere near as reliable as a Honda and too thirsty (head said Honda, heart said something less rational...). So, it will either be a Euro, or an Integra vti-r, or a late model Prelude (though these seem a bit thirsty?). The Euro does seem a more ‘grown up’ car, and less likely to have been thrashed (though Hondas do seem almost immune to ‘thrashing’, so long as they’re otherwise looked after...).

Regards,
John.

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Originally Posted by aquasurf

My story of the rev hang fix is here.
The VSA fix was simpler but different.

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Aquasurf,
That's good, but rather generic and beyond the scope of most (certainly myself...).
If I had a rev hanging Euro, what could be done tomorrow to address it...?
What hardware would be needed? What other changes? What would it cost, and who would I give the $ to??

Regards,
John.

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Originally Posted by JohnL

….The VSA mod sounds interesting, but is it this that has addressed the rev hang issue? If so how? If not, then what did you do??...

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The VSA mod is separate from the rev hang delete I implemented by the connection of my QREVS module. I did use one function of that module to trigger my VSA activation speed threshold (30 km/hr.) to re-engage the VSA after reaching it but that was just for convenience, it could have been handled independently by the gearbox speed sensor signal. Otherwise the VSA mod is just a collection of 2 timers and some relays - in fact it is very primitive but it does the job. How it works is that after ignition on and engine running the timer waits for 1.1 second to switch on contacts of the VSA dash switch for 0.5 sec. (basically the same action I used to do by hand before) to deactivate VSA before launch. When speed is reached, different timer switches on the same contacts for another 0.5 seconds to activate the VSA. When speed drops below the speed threshold, the VSA switches off again in readiness for another launch.

From your description of mods you did I see that you are REALLY interested in improving your cars. I wish you luck in finding the right next "new" car. If you had a chance to read my rev hang website you would see that the rev hang delete module I built is universal and suitable for many different cars. The hardware remains the same, only the software differs. I proved it by fitting it to 2 different cars (2013 Yaris 1.5 and 2012 Accord Euro 2.4). I did not expect the general skepticism of car owners complaining about the rev hang in their cars that I have encountered online in different Forums when I wrote that the rev hang can be fixed. So it was a pleasure to come across you who understands what needs to be done to stop this dreadful malaise of modern motor cars. Perhaps we will meet one day. Cheers.

Oh sorry, I missed your other post. To fit my module you would need to identify pin assignments of your ECU (revs, speed, clutch switch). I know these for the Yaris and Accord Euro but not for other cars. Then I would build one module for you and provide instructions how to connect it. About $200-300 should cover the cost. I might even come to visit you to help fitting it.

Aquasurf said;
“From your description of mods you did I see that you are REALLY interested in improving your cars.”

Yes, I’m an inveterate tinkerer, always think it could be better...

Somewhat off topic, the CB7 (related cars, and I assume the Euro) is a very good base due to its superior suspension geometry, but let down by a general softness in the set up (probably not so much the Euro). I found that stiffer springs and dampers, and a stiffer rear ARB really do make a big difference (as does deleting the front ARB, i.e. reducing front roll stiffness relative to rear roll stiffness, which reduces understeer, so long as total roll stiffness is high enough that roll motion is not excessive).

I’ve also changed some of the bushings (e.g. the front lower control arm ‘silentbloc’ bushings are now much stiffer items from a series one Land Rover (spring shackle bushes), with adaptor sleeves to make them fit. The upper wishbone bushings are from a Commodore Panhard rod. The rear lower control arms are shortened arms from a Corolla (which have much stiffer rubber bushes than the stock Accord bushes, and as a side benefit allow simpler rear toe adjustment). The steering rack housing is also braced laterally to the sub-frame. The caster angle has been dramatically increased. Wheels are wider prelude rims. All this helps, a lot.

A torsionally stiff chassis is very important, but the CB7 chassis is not as rigid as more modern cars (ANCAP rating driven I think), so front and rear strut braces do make a noticeable difference, sharpening up the steering and chassis response. Also, many not so ancient cars (including the CB7) are weakened by lack of panelling behind the rear seat (deleted to allow an aperture for carriage of long cargo, hence fold down rear seat backs). I made an ‘X’ brace to fit in this aperture, which was about as noticeable as the change made with the rear strut tower brace. Since more modern cars tend to have much stiffer (and heavier...) chassis, much of this stiffening is likely to not have as much effect with a car like a Euro.

With all these mods the CB7 makes a fine sports sedan, would be even better with an H22a Prelude engine and gearbox...

“I did not expect the general skepticism of car owners complaining about the rev hang in their cars that I have encountered online in different Forums when I wrote that the rev hang can be fixed. So it was a pleasure to come across you who understands what needs to be done to stop this dreadful malaise of modern motor cars.”

Marketing a new idea is very hard. I suspect a lot of people won’t be interested because it doesn’t increase actual power. Many may want to see independent evaluations and / or endorsements from a famous face. Many may want to see a known brand name, or at least “made in Japan” on the box. Many may fail to detect a ‘cool’ factor. Many just won’t see what the fuss is about. In my experience some people get the rev hang issue, and some insist it’s just a characteristic and not a problem, once you “learn to drive the car properly”. Of course they are missing the point...

“Perhaps we will meet one day. Cheers.”

Perhaps, where in Sydney are you?

“About $200-300 should cover the cost. I might even come to visit you to help fitting it.”

Sounds reasonable to me. I’ll keep it in mind, but first I need a car to use it on....
Regards,
John

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Originally Posted by JohnL

..... I’ve also changed some of the bushings…

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Some years back I changed rear drums to discs in a Suzuki Swift 5-speed, upgrading it to GTi specs and also fitted new bushes in the rear trailing arm and installed a rear sway bar where there was none. The car handling was then much improved and even my daughters, who both learnt to drive in it, loved the Suzi and were sad when I sold it.

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..... where in Sydney are you?

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I live and work in Illawong in the Sutherland Shire. Over the course of several days I kept driving with a video camera in my Euro recording engine revs in dependence on the throttle pedal position and gear selected. I then created a series of graphs documenting the effects of rev hang and improvements achieved by my Qrevs box. I expected the Euro to be more badly affected by rev hang than Toyota Yaris I tested earlier and was not surprised to find this true. The Yaris was not too bad in this respect as I chose to buy it because of its docile characteristic. The Euro was its opposite as I bought it in the knowledge it was affected to a significant degree and believed I would be able to fix it. I was playing with the car for less than a month and I am finished with it. The Qrevs firmware version for Honda K24 engine is on its final itiration.

With all the data collected I also created one graph showing why the rev hang suffering cars jolt and buckle when gears are shifted quickly at high revs. For those interested I placed the graphs at the end of my rev hang website.

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....Many just won’t see what the fuss is about. In my experience some people get the rev hang issue, and some insist it’s just a characteristic and not a problem, once you “learn to drive the car properly”. Of course they are missing the point...

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I follow many websites dealing with this matter and it looks like there are quite a few people who dislike the rev hang. Owners of major brands, like VW and Subaru in the States even went to the trouble of organizing online petitions calling on the manufacturers to do something to ease their pain. It is said that the VW petition already has over 250 signatures but I think we know that car manufacturers' hands are tied. Their solution in the USA seems to be to discontinue offering manual gearboxes. Sadly, even the latest Australian sold Accord, after the Euro was discontinued earlier this year, is only available as an auto.

Well, the cars still available with manuals will probably all suffer from the rev hang in years to come. Some of their older owners who remember the good 'ol times of carburetors and cable throttle before the rev hang existed may be interested in fixing their new rides. The younger generation will simply accept them as they come. I found a working fix for my own benefit in the first place. Should people become interested in it also, I am in position to help them. How does the saying go about building a better mouse trap …?

With my gadget being universal, it would probably work even with your CB7 and you could later transfer it to your replacement car. I know you wrote about experimenting with the idle circuit and experienced minor drawbacks with low idle at higher parasitic loads, like A/C on. I do not think my Qrevs box has any drawbacks like that :-).