exhaust cam retarded one tooth and stutter box is uncontrolable!!!

[RacethisTSI]

talked to a few sources about my fp 2x cams and everyone told me that retarding the exhaust cam one tooth on the cam gear would give me the best top end. the car is running front wheel drive times, just went to the track lsat night, and with a 1.8 60 ft hitting all my shifts and trapping a 127 i pulled a 13.0? . but going off the line the studder box will build boost like crazy then flood my car out..i mean like 30 lbs within 2 seconds. im looking for somone running these cams because the car is getting retimed tommroow and im going to set it back strait. let me know what you guys think..thanks

 

[Coup D E'Tat]

Did you notice any difference in spool? Was your head or block ever decked? You retarded one whole tooth on the stock gears, correct?

Sorry I dont have any advice, I'm just a guy who was considering doing the same thing.

 

[pneumo]

...but going off the line the studder box will build boost like crazy then flood my car out...

I'm not sure what this means, but it sounds like a critical piece of information. Do you mean it looses power once under load? Could you explain please?

 

[RacethisTSI]

I'm not sure what this means, but it sounds like a critical piece of information. Do you mean it looses power once under load? Could you explain please?

yes. as soon as i let the clutch out, it floods and the car takes about a minute to get back to normal running...i didnt think a studder box was supposed to biuld this much boost...30 psi within no time.



and yes i retarded one tooth on the stock cam...i dont know if it worked untill i try it at stock settings... im just trying to figure it out because right now im pissed about the times its putting out... i guess its funny though 13.0@ 127 the cars deffinetly got top end now...turbo lag is a huge enemy, theats the only thing i can think of for teh times

 

[RacethisTSI]

wow, i dont know what changed from yesterday to today but dam... went to launch it today and i had 4 40 ft patches....only thing i can think of is because its a dsm...

 

[95blackGsTurbo]

To much overlap from retarding the cam is going to take away from your bottom end significantly. Will add to the topend but will take a lot away on the bottom.

 

[Coup D E'Tat]

wow, i dont know what changed from yesterday to today but dam... went to launch it today and i had 4 40 ft patches....only thing i can think of is because its a dsm...

So, any answers to my previous question then? I'm really interested in doing this if it'll keep my SC61 from surging.

 

[RacethisTSI]

i dont see how taht would pervent surge...i just did it to get the entire exhaust pulse and then some to spool the turbo a bit...i noticed a slight increase....but nothing major...maybe 200 300 rpm sooner

 

[GVR4592]

One tooth on a stock cam gear is roughly 7 degrees if I recall correctly. That's probably too much for your setup.

Do you have the anti-lag turned on in Dsmlink?

 

[olmytsi]

How about posting a log?

 

[Coup D E'Tat]

i dont see how taht would pervent surge

Well, that's why I was wondering how the turbo spool changed.

 

[jo1]

The surge is from the turbo (SC61) not the engine... retarding the std exhaust cam is to counter the bottleneck in the head when using higher flow turbo

 

[GVR4592]

The surge is from the turbo (SC61) not the engine... retarding the std exhaust cam is to counter the bottleneck in the head when using higher flow turbo

Retarding the cam won't affect a bottleneck in the head. If there's a change in powerband from cam timing changes it's due to cam opening and closing points in the combustion cycle.

 

[BISHILVR]

Retarding the cam won't affect a bottleneck in the head. If there's a change in powerband from cam timing changes it's due to cam opening and closing points in the combustion cycle.

Thats right, the changes will be in the cylinder filling and evacuation efficiency at different rpm points in the rev range.

 

[Coup D E'Tat]

Well, my theory matched Luke's. I figured if I slowed spool (change in the exhaust gas energy,) it'd move the airflow down the compressor map a bit, and hopefully stop this damed surging.

I think I need to bite the bullet and just order a ported T04E cover, but I hate the thought of it, especially on a journal bearing turbo. Maybe something is just wrong with my setup, who knows.

 

[BISHILVR]

Well, my theory matched Luke's. I figured if I slowed spool (change in the exhaust gas energy,) it'd move the airflow down the compressor map a bit, and hopefully stop this damed surging.

I think I need to bite the bullet and just order a ported T04E cover, but I hate the thought of it, especially on a journal bearing turbo. Maybe something is just wrong with my setup, who knows.

I think what your thinking of is when some guys will allow some of the combustion to take place in the turbine housing to release energy and spool the turbo a little faster.

 

[jo1]

Thats right, the changes will be in the cylinder filling and evacuation efficiency at different rpm points in the rev range.

cylinder filling and evacuation efficiency is not a bottleneck to the stock head with stock cam and big turbo?
try running a big turbo and stock head without retarding the exhaust cam at higher boost.. then you will know.

 

[GVR4592]

cylinder filling and evacuation efficiency is not a bottleneck to the stock head with stock cam and big turbo?
try running a big turbo and stock head without retarding the exhaust cam at higher boost.. then you will know.

I just realized you're talking about stock cams. We are talking about FP2x's, they aren't a bottleneck with his setup, and neither is the stock head. The stock head has made over 650whp on a few cars, I don't think it's a restriction at his power level. Cam timing can affect the powerband and peak power in a big way, but retarding the exhaust cam is not a requirement for high horsepower.

 

[BISHILVR]

Correct again!

 

[jo1]

opss....

seem that the setup is more than less like mine and maybe there is a solution with my problem as well... or is it SC61 is surge prone turbo because of the compressor trim and housing?

 

[brute]

Well, it does not have an anti-surge compressor housing. He already said that he should just buy a T04S or comparable anti-surge housing. I agree with this. Do it if you have the money.

 

[RacethisTSI]

so really retading the cam has no effect with a big cam, except were the power band is?..so by doing what i did..i moved the power band to a higher rpm? if thats the case i need to retime the car, that could also be the problem with my quater mile times, too much lag from the power band being higher?

 

[RacethisTSI]

and yes my anti lag is set up through dsm link

 

[GVR4592]

so really retading the cam has no effect with a big cam, except were the power band is?..so by doing what i did..i moved the power band to a higher rpm? if thats the case i need to retime the car, that could also be the problem with my quater mile times, too much lag from the power band being higher?

Nobody said it didn't have an affect. I said it wasn't required to make big power. I also said if you retarded it one tooth on a stock cam gear that's way too much. Set it to stock and go from there.

What is your timing fixed at with the Dsmlink antilag settings?

 

[1SloColt]

Well, my theory matched Luke's. I figured if I slowed spool (change in the exhaust gas energy,) it'd move the airflow down the compressor map a bit, and hopefully stop this damed surging.

I think your theory is correct. Friend of mine on a 35r with ported shroud is seeing compressor surge ever since he threw on a CAI, which actually improved his spool around 200-300rpm according to the AEM logs. Without the CAI he didn't have surge issues because the spool up was in an RPM range that avoided the surge. He's now going to have to go to a larger turbine housing to slow spool times in order to avoid the surge, from a .63 to a .82 t3 housing. We tried to decide if larger cams than his current 264/272 setup would cure his problem but came to the conclusion that it just wasn't enough of a bottleneck with the current cams to try larger cams.