Just so we could all be on the same page, could we all decide upon the definition of "load"? In this case, are we talking about manifold pressure? static MAF voltage? Rate of RPM rise?

Shiv

 

Mine would be the resistance to engine acceleration. Each successively higher gear takes longer to wind through, and that is because of both the gearing ratio, and the resistance to rolling, and aero.

 

Very valid but this could also be simulated by dyno testing in a higher gear (with a Dynojet) or with a slower ramp-up rate (with a load bearing dyno), correct?

Shiv

 

Absolutely, on the street it would be easy. My point is that on a dyno you can't simulate the street, unless the dyno were programmed with the cars' coefficient of drag to calculate the aero resistance at a given road speed.

 

Thanks for the info David. I think we both found the problem with your dyno testing. Depending on at what RPM you start the run at, the spool up characteristics of the turbo and the weight of the dyno roller (224 or 248), doing a 2wd dynojet pull with a 393whp car, in 3rd gear, would result in a full boost time of 5-6 seconds before you hit the rev limiter. It is understandable that there could easily be enough thermal mass in an intercooler to keep outlet temps low for this short period of time without any help of cooling fans.

However, if one were to extend this full-boost/WOT condition to 7, 8, 10, 20 seconds, etc,. (and perhaps do successful back to back runs without very long cooldowns), the cooling efficiency of such an set-up would be greatly compromised. Along with it, the dyno's ability to replicate real world conditions.

And that's for a 400whp car. On the 600whp car you were talking about, the full boost/WOT condition would probably last only 3-4 seconds before the rev limit. I can't see how such a test could replicate anything close to the kind of testing conditions one could see on a road.

Just my 2c,
shiv

 

A dyno with the ability to control ramp up rate (any load bearing dyno) can do just this. No real need to bring Cds into the mix. Just test using different ramp-up rates (dMPH/dT) As long as the air is true and the engine/intercooler/radiator see realistic temps, you will have perfectly replicated real world conditions.

shiv

 

Maybe I am just confused. (Quite likely by the way) When a car is tuned, does the computer change the injector pulse at wot based at all on wheel speed, or is it just rpm, air flow, manifold pressure,and air intake temperature based. My point is that the ramp up rate that you are talking about would change for each gear. If you tuned the car in 3rd gear on a dyno, with a ramp up rate that you found corresponded with matching air/fuel ratio's when road tested in 3rd gear, would the results duplicate if a subsequent dyno run was made in 4th gear, and then taken for a road test in 4th gear? I could very well be wrong, but I would think that the afr's in 4th gear would then not match each other. Might be an interesting test to make.
Mark

 

ECUs typically adjust injector pulsewidth based upon MAF, RPM, intake temp and baro pressure. Coolant temp does come into the mix as well when they are above and below "normal" operating temps which is usually considered to between 80 and 100 deg C. Wheelspeed input can sometimes be used by some ECUs to limit boost at lower speeds. This is the case of turbo Subarus where their top mount IC doesn't work to well until vehicle speeds are above a certain level. Many 2wd turbo cars also reduce boost in the lower gears for traction reasons as well. In the case of BMWs, Mercs and some other vehicles, wheelspeed can be used (in conjuction with RPM) to determine what gear is being used so that one can have different fuel cuts in different gears. Same goes for max speed limiting.

But as far as basic fueling goes, wheelspeed is rarely a usuable input since it doesn't have a constant/fixed relationship with engine load. Imagine how simply driving up or down a hill (or even with a head or tail wind) will throw off things off. Needless to say, MAF and air intake intake temp do a better job of measuring actual engine load conditions.

Hope that clears things up.

my 2c,
shiv

 

Yes it does. Thanks.

 

[cough] ...not really, although 4th gear @ 80 is seen more frequently.

l8r)

 

If you have an air temp sensor on your upper IC pipe you will see that intake air tempnat the throttle body goes up durring a long WOT pull, and water temp also goes up.... but the air temp increase is much more substantial than the water temp change.

Keith

 

Thanks for your input on this topic. I didn't mean to open a can of worms by bringing up the road VS. dyno tuning issue. What I was trying to find out is if anyone would say that they think a "Mustang Dyno" style system would more accurately simulate road conditions than a "Dynojet" style dyno.

David did say that he preferred to tune on the road because he is aware of the difference, so there is no need to come across like you are telling him he is doing something wrong.

Shiv, it sounds like you are arguing about David's dyno methods. Please, let's try not to hijack this thread. Every tuner has their differences of opinion on how to tune. That's what makes this country and this sport so fun - everyone has free will to choose with which company to spend their hard-earned money. People can choose a tuner/company that they see eye-to-eye with. If everyone did things the exact same cookie-cutter way then we would never see the level of innovation that we do in this sport.

So one company can make 400 or 600 HP without using a fan, and another company can make those numbers using a fan. Doesn't really make a difference to me.

I just know that this has been the most informative and enlightening thread I have read. Shiv, are you working on something similar with Vishnu parts?

EVOlutionary

 

Well said

 

My EMS datalogs always show my A/F ratios getting richer at the same RPM as the car goes through its gears. My assumption for this has always been that as the car is making a pass, intake temps are going up. So when air gets hotter, there is less oxygen. The EMS does not know what gear the car is in so it just supplies an amount of fuel based on RPM and load. If these conditions are met, then the car should get richer as the temps get hotter because it know no different.

There are modifiers in the EMS to compensate for these conditions. You could set a modifier to pull x% of fuel out as air temps rise. This would allow you to keep the A/F more consistent through each gear.

 

this was david's post:

To duplicate this exact set up on another EVO the break down would look like this:

Buschur Racing Stage 4, this is minus the AFC, $3430.
AEM EMS, $2400
Ported intake manifold, $75
BR 65mm throttle body, $300
Ported exhaust manifold, 02 housing and turbine housing, $300.

This is what is making the power in the car, total is $6505.



Was this with the 264/264 cams?