First Time 1/4 Mile with a Turbo Charged D-series Hints??

[Lukezen27]

Luke, post up your dyno graph again.

Sure

[CRXer]

go in the WSID reflections thread luke,the links in there to the pics & theres also a another pic of u in that thread too,hope u dont mind me posting pics of the turboD

BTW,u guys are forgetting a little about the small capacity NA engine,especially the likes of the B series,its easy to bog these motors down,its all about airflow efficiency across the head,& too much throttle abuse will lead to poor power output trying to get an NA going.

[CRXer]

Thanks for that mate. I didnt actually know much about Anti-Lag and how different systems worked. Only What the feature was and the benefits of it.

Rep for u!

Just be careful when talking about the benefits of it,most motors that use antilag are throwaway motors like world rally cars,hipo drag motors,etc.They know they are chucking the thing in the bin after 1 or 2 events so they dont care about the consequences.

[Sexc86]

I have drawn up a few graphs to help represent and explain better the point I have been trying to make.

The three graphs
1 – NA
2 – Common FI
3 – Ideal FI

The graphs represent 3 factors.
* X axis – Time in Seconds
* Y Axis (left) – Boost Pressure
* Y Axis (Right) – Power % @ RPM

All these graphs are basic on simple even generic numbers, as well as all figures I have given in examples. Purely illustrative..

Aim – To show the effects of boost lag and driving style in any forced induction manual car. How this may or may not affect your MPH & ET. How this is comparable to a naturally aspirated setup of similar spec. How ET potential cannot be as simply predicted on a FI setup as a NA setup when looking at MPH and 60foots.

First graph (Shown below – Common FI). 90% of forced induction newbie drivers are like this, unable to launch on full boost and unable to sustain full boost after gear shifts. As I have shown, once boost has reached its target of 10psi (in any gear) it is at 100% power at its given RPM. Don’t get mixed up with peak power on a dyno-graph, completely different. Once there is a slow shift, boost pressure is lost. Upon engaging into the next gear, this boost has to be built back up to full boost or 100% power at RPM. This takes time. All depending on your turbo size, engine capacity and boost setting. Can be anywhere between .5sec – 1sec. This happens 3 times in a drag. This means up to 3 seconds you are waiting for boost pressure to get back to 100% power at RPM.

Graph Common FI


FI VS NA

Example. Two cars both exactly the same in every way. All conditions equal. Both make 100wkw Peak power. Car A = FI – 100wkw @ 10PSI, Car B = NA 100WKW @ 0PSI.

Car A is accelerating at WOT. Full boost at 10psi. Driver gets to 6000rpm and is making at this stage 90wkw. Driver releases throttle. Blow of valve releases. All Air pressure escapes. Driver puts is foot back on full throttle. At Which instant point he is still at 6000RPM but 0psi. Hence he is not making 90wkw anymore. Closer to 60wkw. Driver continues to accelerate. Boost rebuilds back to 10psi but takes 1sec to do so.
Hence he is not always at 100% RPM power.

Car B is accelerating at WOT. Driver gets to 6000rpm and is making 90wkw as well naturally aspirated. Driver releases throttle. Driver puts his foot back on full throttle. Car B is instantly still at 90wkw @6000rpm. Hence he is always 100% RPM power.
This is an example of how in a drag race a NA setup will always be in 100% RPM power. It’s constant (Shown below - NA). But with FI it will depend on weather the car can be launched on full boost and if full boost is sustained over shifts. That’s why MPH can change so much with FI as the percentage of time (out of the 15sec of less) spent in 100% RPM power can vary considerably (all due to driving style). 50% of the time in your race up to 100%.

Graph NA


The main aim of all ¼ N/A drivers is of course. Quick launch, Quick shifts and efficient power delivery.

The main aim of an F/I Driver is all of above. As well as a not having to ever build up boost at any point in time as soon as you leave the line. Ideally it needs to be there 100% of the time.
I.e. Graph “Common FI” needs to become close to graph “Ideal FI”. (reducing the boost lag gaps on launches and shifts)

Some may never get to this stage (100%) based on human driving skill (shown below – FI Ideal). That is why there are features like Anti-lag, flat shift and launch control. As well as people using the hardcore 2speed auto boxes, where you’re never going to loose boost, due to never having to release your foot from the throttle. (Peg leg?) (Stall/torque converters?)

Graph Ideal FI


Don’t mix this up with power delivery to the ground. This is engine power output.

Apologies as this may be hard to follow for some people. I have tried to explain it to the best of my ability, and some of my terminology maybe different to conventional measures. Look forward to some reply’s

To conclude, IMO I believe it’s easier to get an N/A cars best possible ¼ time much easier then one of similar FI spec. I also believe that it’s easier to predict futures ETs from N/a MPH that that of FI setups.

[90LAN]

I dont speak JDM.

i dont speak audm

[fatboyz39]

this thread is funny. Lyle, have to give you some credit for trying.

[EKVTIR-T]

sounds like a spaceshuttle launch lol

[CRXer]

Lyle,yes much credit for trying.

As i said earlier,its just as easy to bog down or "lag" a small capacity NA motor upon launch & shifting,particularly multivalve,multicam head designs which make their seemingly extraordinary power from high air flow efficiency.

If u go just dropping the throttle closed(or even any part thereof can cause the same problem) during shifts,u upset the flow pattern dramatically & turbulence doesnt just disappear instantly like u seem to think.The same sort of concept for FI,u go relying on your blow off valve to keep your turbo spooled upon just jumping off the throttle at will,u'll probably never win.U gotta keep the air flow smooth with NA,u gotta keep the turbo producing as much pressure as it can muster with FI,same shit,different smell.

I did exactly what im talkin about a coupla weeks ago.First run was half asleep as usual,just jumped completely off the throttle going into second like i was still pottering between traffic lights or similar,the motor bogged like its never bogged before,seemingly took ages to sort out the air flow again & start making its most efficient power for the given rpm.Result..........FAIL.

Its only the most efficient, best of the best NA cylinder head designs that will allow u to just jump on & off the throttle at will,this includes all the bolt on gear to go with it,its called response.

Same thing for FI,the best of the best,eg WRC with their elaborate antilag control & turbo setup designs,will only allow u to mash the throttle at will.

So get out there & see what u can produce out of one of our small capacity NA setups before u downplay it as being so goddam easy to do.

[EG5]

Tyre sizes , gear ratio , suspension set up ,traction bar set up , Tyre choices ( Drag Radials , Slicks etc ) play a big part aswell when you launch it off the line.
I tried too many different combination of launching , suspension set up , tyre sizes , gear ratio , tyre pressure etc. Put all those things together and lock it in so you know what will work or not.

Practice makes perfect , thats all I can say. Good like with future runs

[Sexc86]

agree with claymore... some people are confuseing power delivery with power output

[Lukezen27]

Man that was a big read lol

Anyway lots to think about while I'm backpacking in Thailand next month

[EKVTIR-T]

Drags aside,enjoy the trip.
Don't forget to check for adams apple first!