Rev hang - a curse or blessing

[JohnL]

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

[aquasurf]

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

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.

..... where in Sydney are you?

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.

....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...

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 :-).