Cant get into boost

[Reignman]

Im in the process of tuning my S14 with RB25 (PowerFC, GT32 turbo, 525cc injectors) Every time I try to go WOT I get to about 3/4 throttle and the engine starts to shudder and I can never get into boost. I thought it was knock at first but the knock is staying low. The A/F ratio is a little rich but it is around 10-11. Im also running a blow through Z32 MAF. Anyone have any ideas on what this could be?

[Blown240sx]

Blow through sounds to be the problem. The blow through setups have a big tendensy to leak boost or destroy the MAF. Id say its leaking boost at a certain point or the MAF is wiggin out.

[Tictakman]

can you sit and idle and rev up the engine? past 3000 rpms?

from what it sounds like you may need to gap ur plugs smaller, do u know what they are gapped at currently?

what is the order of ur intake system?

fliter-turbo-ic-maf-bov-throttle body?

[Reignman]

can you sit and idle and rev up the engine? past 3000 rpms?

from what it sounds like you may need to gap ur plugs smaller, do u know what they are gapped at currently?

what is the order of ur intake system?

fliter-turbo-ic-maf-bov-throttle body?

I can rev the engine past 3000rpm without problem. Right now I have the plugs gapped to .8mm.

Intake system order is: filter-turbo-bov-ic-maf-tb

[Reignman]

Blow through sounds to be the problem. The blow through setups have a big tendensy to leak boost or destroy the MAF. Id say its leaking boost at a certain point or the MAF is wiggin out.

This might be the problem. I did put silicone around the maf when I first put it on but I wasnt able to get it on certain parts because it was already mounted. I also just noticed that my vacuum at idle has gone from 20 to around 15 now. I might have a leak at the maf. The maf is reading fine so I might just need to seal the housing better.

[Carl H]

yah ive found that most mafs will need to be 'boost prepped' to hold any ammount of pressure.i blew mine apart when doing a light throttle load and didnt notice it till i stopped and happened to look in the fenderwell and see that the cover was nearly off.

[Reignman]

yah ive found that most mafs will need to be 'boost prepped' to hold any ammount of pressure.i blew mine apart when doing a light throttle load and didnt notice it till i stopped and happened to look in the fenderwell and see that the cover was nearly off.

Carl, what did you do to your maf to hold boost? Did you do anything other then sealing with silicone?

[cdorhout]

I run a Q45 MAF blow through, and I've had no trouble so far, up to 13psi. To (boost prep) mine, I just filled in the gaps with silicone, and then put a few cable ties around the MAF so it couldn't expand or blow the cover off.

[Blown240sx]

Im not saying it wont work cause I used blow through for a while also but Ive read to many stories how the MAF burns outmuch faster due to the pressure of boost.

[Reignman]

Well I sealed up the maf but still having problems getting into boost. Heres the wierd thing. I have a Q45 TB and I adjusted the tps along with advancing the cas a bit and I could get into boost after that. The problem I have now is that with the cas advanced the car idles up and down when Im off the throttle and when I try retarding the cas I cant get into boost again. I wouldnt think the base timing would effect getting into boost. Any ideas on this?

[cdorhout]

I'd first of all get a timing light on it and get the timing perfect. 15 degrees advanced at 700 rpm.

Then check fuel pressure, set to 43.5 psi.

My car ran like **** for a long time until I finally checked the timing with a light and found i was running 5 degrees retarded.