I remember reading that the dyno numbers for a stock EVO can vary +-10hp. Do you have any idea why such a large variance? is this normal for other cars?

 

Yeah, Why is that? I noticed that too. Some people on highaltitudeimports.com dynoed their evo's and the stock had a variance of as much as 15 hp.

PS
Shiv got your PM. I am in italy now so kind of tough calling there. I will try when I am back in the US.

 

The variance is even larger than that. And our sample pool of 30+ EVOs is pretty large by most standards. Test in 4th gear (closest to 1:1 ratio), the lowest has made 165-170 wheel hp, the highest has made 200-205 wheel hp. The 165-170 whp car is certainly an outliner though. Most of the cars range from 180-195 wheel hp.

FWIW, we tested 2 STis yesterday. One made 210 wheel hp. The other made 235 (!) wheel hp. Most of the others we've tested make right around 215-220 wheel hp. The only one that didn't detonate audibly during the run was the one that made 210 wheel hp.

As for the variance, I'd say a lot has to do with motor tolerance. Small differences here and there can have a pretty significant impact on knock resistance. And since these turbo cars make max power right at their knock threshold, a more knock prone car will run less timing and make substantially less power. 1 deg. of retard can easily equal 10-15 wheel hp, all other things equal.

Cheers,
shiv

 

isnt 170-185 less than a stock WRX? i dont get it they are like 190 whp or is that like the high end of the curve for them?

 

thanks for the reply shiv.

on shiv's dyno WRX's are around 160 (correct me if I'm wrong)

 

Hi Shiv,

How does the ignition timing variance look on the stock evo? Did you try to reset the ecu on the weaker cars, so perhaps it is able to gain more power? I'm still puzzled on the huge horsepower variance between different evo's. Perhape your xede will close the gap on the ecu side.

I still don't understand how engine tolerences is that bad? Could they messed up on cam timing or something else. I can see 10 hp between engines with your tunned ecu but 40 wheel hp between the weakest and stronges is ridculous. Perhaps it's the 91 gas messing the ecu's?

 

It's definitely not octane related as we saw just as much variance with cars running 93+ octane levels at the MD Dyno Day a little while ago.

Mark

 

GTR's right....40 wheel hp is huge. What's the distribution of EVO's like from 165-205hp (ex. 90% of the 30+ are 180-185)?

 

You see this type of variance with most cars but the turbocharged ones running on crappy gas tend to have the biggest ranges. Also the ones that are broken in (10k miles or so) will make more power. Theres quite a few variables but it boils down to some cars are strong, some are weak, but most are right in between.

 

We have not seen that kind of variance with the road dyno. I'm not implying it is more accurate, and our sample pool is much smaller. Five cars have all been within 5 to 10hp corrected for temp and humidity. Which I would consider pretty consistant and within the resolution of the Road Dyno.

I wonder how much of the variance from chassis dyno's is "roller loss" etc?

Speedlimit...


Also, have the AF ratio's from the Works dyno pulls been posted?

 

Why is it that Shiv is always harping on the issue of Evos having a problem with detonation??? Not that I'm saying it is not to be concerned about. On my Evo here in Texas at 100 degrees (93 octane), when I had the restrictor removed next to the BS, and boost spiking to 1.46 bar, I never heard a single knock or ping. The plugs looked fine after cut off...

 

I haven't seen any of detonation either and we've been running Evo's at many track events for extended 25+ minute sessions in 95+ 'F heat with no problems. And this is in Evos making 225whp stock to 340whp modified. And the brakes have been fine and the clutches have been fine too.

Maybe we're too busy enjoying life and the Evo's to waste time looking for problems, that might just not be there.

 

You can't always hear detonation and the ecu adjusts for it, which in turn will cause it retartd the ignition timing and effectively cutting power.

 

Exactly. Most modern turbo cars won't detonate due to knock control systems. But that doesn't mean that they don't loose power when heat soak sets in. Do a few back to back runs on the dyno (even with high velocity airflow pointed at the radiator and IC) and don't be surprised if output drops substantially. Even without a dyno, watch ignition advance on a scan tool and see if drop with each successive pull.

Cheers,
Shiv

 

OK, I'm getting old and hard of hearing, but I think that even if I had extremely good hearing, I might not detect engine knock without a knock sensor and display. In the old days, the big V8s would knock and it would sound like a dozen marbles rattling in a gallon metal bucket... Very loud, no mistaking for anything else. However, with my Miatas I could not hear the knocking that the J&S knock sensor and timing puller would detect!... Later, I learned a very expensive lesson with my supercharged Integra. I never heard or detected the knocking that must have happened to blow one of the cylinders in the engine. I'm not taking chances with this again. I'm going to use every tool and technique at my disposal to make damned sure my car does not knock or run with excessively high EGTs.....