Hey everyone,
I recently got some more toys put on my 04' 6mt coupe but unfortunately the numbers weren't that great.

In January this was the setup:
Mods: strupp Headers, kinetix y-pipe, crawford v5 plenum, jwt intake w/ z tube. Stock exhaust.

1/17/06, 57 degrees, Humidity at 42%, SAE 0.94
Power= 248.61 Torque=240.55




Last week the dyno was done with all the above mods in addition to Crawford High Flow Cats, Crank Pulley, Unichip

8/10/06, 80 degrees, Humidity at 43%, SAE 0.99
Power=246.49 Torque=232.58


I was hoping to reach high 250's with these mods or barely gettin over 260 rwhp. If I can get some advice as to what the problem may be. Is temperature a big factor in the loss of HP and Torque? Or does anyone have a setup similar to this or knows where the problem lies in my set up where the car isn't getting its peak performance? Thanks for the tips!

 

im pretty sure youll get better results if you re-dyno with the same mods again when its cooler

 

Stillen proved it to me...they did dyno on my car.....5F different in coolant temp result in 10whp

 

SAE corrects for the temps and other conditions (baro pressure, humidity).

 

Odd, because I've run my car at the track (about 20 passes total) and there is no real measurable difference in trap speed (the indicator of available HP) if I make a back to back pass on a scalding hot engine or if I let the car cool for over an 1 hour. On the same track day, my trap speeds vary by less than .5mph. If the ECU was truely that dependant on coolant temp, I'd expect to see my trap speeds varying by 1-3mph depeding on how hot or cold the engine is.

 

SAE does, but it cannot correct for anything the ECU does, like pulling timing.

 

In close to stock form, I noticed the coolant tempts remained pretty stable. When I was testing, my temps were right at 190 degrees, in bumper to bumper 90+ degree traffic. That was with the a/c on(conversively, the electric fans). With the a/c off, the coolant would quickly escalate, the fans would come back on, the temps would stabalize, the fans would cut off, and a new cycle would begin.

 

I assume you also had a proper unichip tune, correct? If so, then the stock ecu shouldn't be getting in the way, which negates the pulled timing argument from the heat.

Do you have your charts, with a/f? Have you datalogged your timing at all?

 

That is kind of the point for the SAE correction. Naturally when temps are hotter, the ECU will pull timing and add fuel to keep the motor from detonating. Every car using an electronic control will do this. Same goes for baro pressure. The pressure sensor relays the baro information to ECU because when pressure is high, more 02 is freely pumped into the motor therefore fuel must be added or else the motor will experience detonation. The SAE correction is the generally accepted correction factor that compensates for what the ECU will do under ambient conditions. However, it is just an estimate. If the motor is scalding hot, it may impact power somewhat, though on the track, my G35 and my friend's G35 doesn't seem to care if the motor is hot or cold because trap speed remains constant.

Concerning this particular dyno, the SAE CFs are wildly different 0.94 vs 0.99 (close to ideal). It appears that the first dyno was done on a day what had extremely good air (high baro pressure) and that the second dyno was under more typical ambient conditions. Though a 0.94 vs 0.99 doesn't seem like a lot, it really is when it comes to dynos. The data tends to get skewed the further the SAE CF gets away from 1.00 (higher or lower). This dyno shows that his car actually made less power with the Crawford High Flow Cats, Crank Pulley, and Unichip. IMO, I think the car is probably making close to the same power it did during the first dyno, but the SAE CF of 0.94 skewed the data a bit. Also, from the dynos I've seen for UDPs, high flow cats, and the Unichip, none of these mods make any measureable power. Unichip isn't a piggy back adjustable ECU. Correct?

Also, wasn't it you that actually saw a small loss with the Crawford high flow cats?

 

I think you're mistaken. I believe the correction factors originate to before the ECU even existed. They correct for the effects of atmospheric conditions on the engine/combustion process itself, not how some piece of electronics might react to those conditions. I'm not an authority on this subject by any means, but that's my understanding.

As for the cats, that was not me. I never dyno'd the crawfords cats singly. At the other dyno location I used last year, the only thing close was when I dyno'd my kinetix cats. In absolute numbers, I did lose a bit of power across the entire powerband with the cats. But it was not the cats. At the same time, I was running a set of tires that was 7 tenths of an inch shorter than stock(basically 3% shorter final drive). The dynojet automatically corrected for this, and I lost power out of proportion for the correction.

 

You're right, the SAE correction factors have been used well before ECU controlled cars were introduced. My point is correction factors for ambient conditions are directly related to the running condition of the car (timing advance/retard, rich/lean A/F, etc). Even carburated cars compensate for ambient conditions by adjusting A/F and timing. They're just a lot slower to react. Also, the most carburators need to be adjusted for winter and summer driving. ECUs don't have this problem.

The Dynojet shouldn't care if you were using a fractionally shorter drive. All the dyno does is measure the time in relation to how quickly the car spins the ~2,000lb roller. I can see slightly different numbers (~5whp) if you ran in 4th vs 5th, but the gearing is quite a bit different than just 3%.

 

Maybe it's more heat sensitive on SC....190F I got 315whp, 185F got 325whp

 

The dynojets calculate a to-the-wheel ratio by comparing the rotational speed o f the drum versus the measured engine speed(rpm). That way, the numbers theoretically should be repeatable no matter the size of the wheel/tire or the gear. Of course, that omits such considerations as wheel/tire weight, tire pressure, different losses per gear, etc.

Regardless, if one dynos in 4th gear versus 5th, for instance, one can expect lower numbers. In the case of my car, I've observed this behavior on two separate dynojefts(two difference models indecedentally). The changes in measured hp so far have been marginal, in the 3 to 5hp range. But the changes in torque have been in the 7 to 12 range.

So, in reality the ratio does in fact affect a dynojet. A 3% difference in tire height, assumably, would have little effect; a much smaller difference than the differences between each gear's ratio, as you've said. So why did I lose power when I dyno'd with the kinetix? Conditions were virtually the same between the dyno runs(about a month apart). The only differences were the cats and the wheels/tires(also tire pressure; weights were approximately that of the stock wheel/tire combo).

It had me stumped. But then I plotted time verus speed, and I was accelerating faster with the change of cats. It was not a small difference. So, if I was accelerating faster(some due to the change in tire height/ratio), why would the dyno say I was putting *less* power?

 

Man, I had nearly the same thing happen to me.

I dynod stock at 234 hp on a dry cold day, and then I had my Stillen dual catback and spacer installed and pulled 249hp on another cold, dry day.

Then I had Alphawerks headers and an Altered Atmosphere reflash done and was hoping to see 10-15 more peak hp.

Now, on this day it was pouring rain, humid and a good 20+ degrees hotter than the first two runs. So, on the pre-tune dyno I had lost a bunch of mid-range torque since the install of the headers but gained about 7hp on top even though the car was now breaking traction at 3.5k rpm in first gear with the headers when it would not do so on the same track previously!

Then, I got the tune done and gained +1hp at the top but got back all of the mid range torque that I had lost from the first time I dynod with Stillen dual catback and spacer! WTF? On this dyno day it was pouring rain and a good 20+ degrees hotter than the first dyno.

So, long story short, I have no idea what my real numbers are, but the car pulls better than it ever has by my feel, so, I guess that's what I'm going with until I get to the track.

 

This is very true. It has also been proving by DaveO as well as MD. Coolant temps and engine temps are very important when dynoing mods and controlling them so the results aren't varied.

If someone tells you different they have no clue what they are talking about.