VT 355 supercharged AFM issue

[shane1]

That's what I was wondering The1 , I see that too and that's why I was thinking its in the calculation as the actual afm keeps reading steady. Back to the dyno this morning see what I can come up with

[The1]

wouldn't be the extra load on the crank from the charger, just enough to give it some issues somewhere?

[shane1]

Wouldn't think so I only loosened the belt enough to drop 3 psi just so it didn't see the airflow of the tight belt . One run is 8 psi the other 5.5

[delcowizzid]

how did you get on

[The1]

he sent me a message this morning, tried the other bin i modded with the second airflow scalar, didn't make any difference, he tried setting fuel cut to 6375 but made things worse, apparently the fuel cut only seems to work properly when down lower like 5900rpm, the RPM reads correctly in the logs so i dont know what the issue is atm with the fuel cut, it's all factory code... i tested on the bench but works fine, all i can think of is ecu problem. Ill try and replicate the RPM, maf, etc etc where the problem is on the bench and see if i can cause the issue to happen when i get time. On that note i think he set the limit back low again and sent the car out.

[shane1]

Pretty much sums it up , unfortunately time is an issue and I will have to give the car back not as good as it could be but the last 500 rpm are becoming way to much of a time burner , try explaining to a customer you spent hours on the dyno for bugger all result doesn't go down well. Been driving it all afternoon checking cruise fuelling etc , it's plenty fast enough just a few wasps short of what the customer wanted. I know if it could turn 6500 plus it would make the power . I might get a smaller blower pulley up the boost and see if the airflow increase causes an issue or whether it is an rpm based issue . I'd like to think it would play up and it's an airflow issue , problem is it's not my own car and playing around with this sort of power when it's not right can end in tears pretty quick. I wish I could just use an 808 on it , as I said earlier the VT is probably THE worst model to tune . Ill post a graph up tommorrow it's going straight up when it hits the limiter!! I did the same engine spec with a haltec on 12 psi made 430rwkw .Im also finishing off a 355 turbo with an 808 and turbo 400 , hoping to make 450plus rwkw with that one .
I'm still open to ideas but the car has to go so I can feed my kids

[delcowizzid]

vl400's 11p will be the one to use soon 3 bar electronic auto code

[The1]

did some quick testing,

found that after 4000rpm cylair caps, no matter how much MAF airflow i feed it, it wont go any higher and you can never reach anywhere near 953 cylair limit, it's only below 4000rpm with more MAF airflow can you reach upto 953cylair max limit, i had already compared the cylair code in the VT V8 to the V6's when i was doing referencing for the next beta version, the cylair code is identical to the v6's. The V6's dont have this issue, i can go anywhere upto max rpm around 8000rpm and still scale the MAF up and cylair will goto 953, tried complete factory VT V8 CJDN bin as well, same deal. Seems once you scale MAF airflow beyond the point of reaching the cap it will throw random 16:1 AFR commanded values out.

So will have to checkout things a little more with time and see what the scaling issue is.

[VL400]

Good to see it can be explained and reproduced I dont think GM ever anticipated aftermarket airflows like this

[shane1]

Glad to see im not going insane then !! Now to come up with a way to fix it as this engine needs more boost and rpm. Let me know if you have anything new to try and ill get it back.