Dyno Questions

JeepJockey

I dyno tomorrow morning at 9:00 at www.delperformance.com

What are some things if anything I should look out for.

I have never dynoed a car or witnessed one in person.

I am assuming 4th gear is best for these cars. What RPM should the run be started at. 2500 seems low to me in 4th. Would 3000 hurt anything?

Any tips would be appreciated.

Mods: CobbSRI, CobbAP MSF Stage 1+

dadasracecar

Start at 3K. In my experience there is little to no difference and it's better on the car. Also, I'd do 3rd rather than 4th for the same reasons. In the end it's just a number and the only value is the difference observed with changes. The absolute value is very questionable anywhere you go for lots of reasons.

Also, MAKE SURE YOU HAVE A FAN ON YOUR IC and that you allow the vehicle to cool down - at least 10 min - btw runs. If you hear knock or ticking during a pull get out of it.

JeepJockey

Cool, thanks for the reply. 3000 just feels so much better.

aaronc7

don't suck, thats my advice.

but yeah have a fan directly over the IC or close the hood. guy at a dyno day i went to put down better numbers with the hood closed. But then again, there wasnt a fan directly on the IC either in the previous runs.

freebird_78

How about a stock map vs v101 series?

JeepJockey

The comparison I will likely do will be between Stock and the MSF map. However I am still unsure on the safeness of doing a dyno run on a map that hasn't had any chance to learn values. Anyone wanna chime in on this, i am not neccesarily concerned about the "runs better after it learns" thing more than I just don't want to damage my car by running a WOT run directly after clearing the learned values.

dadasracecar

I honestly don't know what the ecu could "learn." The flash should be the optimal settings and the "learning" should be to adjust fuel trims based on deviations from the optimum - sensor not reading right, etc.

I don't know who came up with whole "learning" thing being important after flashing. If anything my car runs better immediately after resetting the battery though the difference is probably negligible.

freebird_78

What the ECU learns is the LTFTs. LTFTs is what is used to correct the open loop base map that is used in WOT. Because JJ is only running an SRI, they shouldn't have to trim much anyways, so learning curve is negligable. If you were highly modded, it would have to adjust much more, in which case it might not be OK just to flash to stock and open it up. Flashing to AP maps should have much less trimming to learn, as these maps were specifically written for the particular mods. This is why most AP guys are seeing relatively low LTFTs. So basically, the lower the LTFTs are after learning for a while, the more closely the map is tailored to your particular set of mods. Obviously the stock map is tailored to no mods, so LTFTs will be off. But again, just on an SRI, it shouldn't be much. I'm running a catted DP, TMIC, SRI and my WOT LTFT are ~8.

dadasracecar

That's not exactly right. The trimming is done to deal with errors or deviations from what is expected. STFTs are compiled and averaged to give LTFTs but they're just there to make the system agree with itself. The most obvious example is the WBO2 seeing stoich when the exact right amount of fuel is added based on the MAF voltage. If it's not stoich, the fuel amount will be trimmed to get to stoich. If this deviation recurs it will be recorded in the LTFT to add or subtract from the amount of fuel indicated by the MAF voltage.

It's purely an error fixing mechanism and if your sensors are operating properly and your mods haven't changed the values, e.g. proper vs improperly sized MAF housing, your LTFTs will be low regardless of mod count.

Finally, unless you have big errors to begin with, a flash should not effect the operation of the car. These cars are relatively new and have relatively few if any mods. Any LTFT will be negligible unless there is a real problem.

The idea that you have allow the car to "learn" after flashing is wrong. If your car isn't running right immediately after the flash, the flash is screwy and you should get rid of it.

freebird_78

The deviations you mention are on account of modifications. Mods like SRI, DP, etc affect the predicted flow rates and therefore AFRs. This is the error that the ECU has to "learn". Again, this is why stock map LTFTs are higher the more mods you throw at it. The more mods you add, the further you are from the predicted flow rates, AFRs, etc, therefore the stock ECU with its stock map has to adjust for those deltas. You are correct, in restating what I said about AP maps. They should be very close immediately after flashing. Again, that is why the AP guys are seeing near zero LTFT for WOT, even after learning. This also explains why it's not a good idea to run maps that weren't designed for your particular mods (running a Stg1 map on a Stg2+ car). Actual vs predicted will be off, therefore LTFTs will have to make up that difference, but only after sampling and averaging STFT for a period, aka learning.

Bottom line, as I stated before, is that a modded car running a stock map should allow a little time to develop LTFTs. A modded car running the appropriate AP map should not have to.

JeepJockey

Sorry guys did no dyno pulls.

Called the guy last week said I have a FWD Turbo car need a dyno DO YOU HAVE A FAN? "Sure we have a fan it is on an arm on front of the dyno"

I fucking get there and the fan is on the wrong FUCKING side ( it was a nice fan to on a pivoting arm whith 360 degrees of rotation could have face that bastard right at the IC). They normally dyno RWD cars and they BACK them on the dyno so of course my car was facing the opposite direction. The dyno is 6 feet in the air and he tells me he will roll in a fan and face it up towards the car LMAO "fuck you"

So Ambient temps at 90 IC temps at 130 and no fan to get them down equals NO dyno for me not wasting that money.

Anyone know of a dyno close to Nashville, Tn.?? This city fucking sucks, if you want to hear washed up honkey tonk come to Nashville, if you wanna dyno your car better go somewhere else.

Aaron if you read this you said you had a friend near Chatanooga know if there are any dynos that way?