Well i just left the shop and we ran into a problem. We installed the scotts performance cams and they sound great on the vq motor but it seems like we are running out of fuel. at 6000rpms the duty cycle is reaching 95 percent(we are running utec). not sure whats causing this. monday we are gonna add a fuel pressure guage and see whats its reading. i'm hoping that we don't need new injectors. good news is that with 10.5mm of lift, these cams are the truth! we turned the turboxs mbc all the way down and the boost is about 7-8psi. can't wait till we get this figured out. if anyone has any suggestions, i'll forward them to my installer. stay tuned, this thing should be a screamer.......for a st.

 

you shouldn't run out of fuel at 7-8psi .. hmm

keep us posted, curious what's causing this.

 

so does the car sound different at all with the cams? that's my next step, maybe.
now you need to get a better wastegate actuator (if you don't already have one). i put one on yesterday, got a retune, now boost holds at 8psi to redline. 377whp on a dyno dynamics (on a 91 tune), which is about 10% more conservative than most, like dynojet.
anyway, good luck with the fuel prob.

 

its not a boost problem.there is a 1psi boost drop maybe. the problem seems to be the HUGE amount of lift these cams have. stuffing more air in my cylnders than my poor little fuel system can handle. we will first try to troubleshoot the fuel system( it ran fine with the unichip, 10.5a/f all the way to redline). after that, maybe get a different regulator and up the pressure slightly. if that doesnt work maybe injectors. i'm hoping its a utec programming issue, since thats the easiest to fix. the cams have a slight burble at idle, at full throttle, these things sound NICE!!!!!!!!!!!

 

"these cams are the truth!" LOL!

Sorry to hear about the problems... I doubt you need new injectors, there are people making much higher numbers with the same APS units. Good luck figuring this out. I was talking to James and Jay last night (early this morning) about your car and it sounds like they have a couple of good ideas... hopefully it will be something easy. As you know, I am no stranger to crazy/inexplicable problems, so I feel for you.

BTW- your car looks awesome! I've always liked the Z better, but ever time I see your black G, I start to question my decision... Truly one of the best looking cars I have ever seen. and your sceen name is appropriate... Your car is likely bullitproof with the 6 inches of wax on it...

 

Just you wait, i'll have that 'silver bullet' covered in wax in no time. yeah, i know its probably something small and i know that it will eat james up until he figures it out. btw, congrats on the tune and numbers, james told me last night. now go forth and boost happy!!!!

 

Thanks -- I was pretty happy with my numbers. Sorry for bumping you off the dyno.

I'll be calling you soon to give my car the full treatment... once this weather clears up. But it will never get as shiny as a well waxed black car. Though I have to say, I was a little disappointed when I saw your car last night... looked like there was a little dust on it. You're falling down on the job.

Again, good luck with your problems... I'm sure you'll forget all about it once you get back on the road.

 

Make sure you rising rate FPR is working properly. It could be something simple, such as a pinched/disconnected vaccum line on the tank based FPR that APS uses.

 

Thanks for the idea Sharif. I think they were gonna hook up a permanent fuel pressure guage in the engine bay for tuning purposes. i'm hoping the fpr didn't go bad on me, but better in the shop than on the road. hopefully on monday they will get a chance to look into the problem.

 

You bought the same cams I used to have.....Good cams....I have a new grind coming....

 

yeah, they sound real nice when the car is on the dyno. i can't wait until i get that baby back on the street. summers coming and its time to be the alpha dog!!! wish me luck.

 

Update: Talked to Ted @ Scott Performance, Nathan @ TurboXS, Tony@ Unichip, and myself (second personality).

Result: TurboXS had the exact same problem w/ the APS ST past 7psi w/ UTEC on stock cams. Fix=larger injectors

I'm gonna verify the fuel pressure is the proper number for the APS 4bar riser. The Unichip works differently than the UTEC. It relys on the increased fuel pressure then trims fuel (alters MAF). The UTEC (in MAP) controls fuel directly by ms, so when the duty is maxed it is impossible to add any more ms. There is no more time available.

Bullitproof is correct.The scott cams are The Truth. The turbo made only 4psi connected straight to manifold presure on the stock cams. Just the cams alone generates 8psi, twice the boost, on mani pressure only. No overlap (what's the point of an N/A cam on a FI car), low duration and high lift totally mutate the typical VQ sound. It's scary!

Correction: TXS had the problem on an APS ST car past 10 psi, so I am assuming a fuel pressure problem. The gauge is goin on as I type. Update to follow.

 

Are the specs of the Scott cams published anywhere?

 

call ted at scotts performance. i don't know their number but i will post it as soon as i find it. they have 3 different specs on their cams as far as i know. i just know the specs on mine and i confirmed it with my installer. but this is off topic. i'm just trying to chase down the reason why my aps injectors are no longer sufficient now that i have cams and utec.

 

my bad, i thought i posted the specs of my cams here already. 242 duration, 10.5mm of lift. low overlap, perfect for forced induction. no shims or buckets required despite the high lift.

 

wow.....super low duration

 

whats your fuel pressure at idle with no vacume to the regulator? Kep in mind the APS INI-Chip set up utilized 58psi at idle of fuel pressure.


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they are installing an under the hood fuel pressure guage to check. we are thinking the way unichip adds fuel and utec are different and we might just need larger injectors. James talked to nathan at turboxs about it and nathan said they had the same problem with an aps st but with stock cams. they had to put in larger injectors. i'll keep everybody informed of the situation.

 

Correction: TXS had the problem on an APS ST car past 10 psi, so I am assuming a fuel pressure problem. The gauge is goin on as I type. Update to follow.

 

I was off the the Scott Performance stage 1 turbo cam specs. It was not bulletproof's error, I delivered him the wrong info. I was close, but not exact. For anyone interested, follow this link. The cams are still bad a$$

https://my350z.com/forum/forced-induction/187575-scott-performance-cam-specs.html