Boost issues
 

Hi,

Well had my FD legally on the road now for a few days and i am loving it, but i still seem to have boost problems. I have search through the site hoping someone would have similar issues but there isnt really anything exactly the same as mine.

So on my 1st turbo its spools up but only hits 0.5-0.6 bar, then the 2nd comes in hits 0.6 bar but then fluctuates and hits one bar drops down to 0.8 bar and then about 0.7 bar, put your foot down again it will hit 0.8 bar fluctuate and hit a bar then drops.

I have check all the IC, Y pipe and turbo inlet pipes and they are not split, checked some of the vacume hoses and all of them seem to be in good condition. So i wonder if its either a pipe collapsing to cause this or a solonoid thrown a wobbly. The car is a 93 Type R with just Apexi filters and Blitz nur exhaust, it still has the cat on it but the car does pop like mad on over run.

Any advice would be good before i start going into the rats nest, i think i will change all the main pipes to hard pipes hoping that will help.

Cheers

Gav

p.s its a JDM import and i am based in the UK, here is a pic of it
http://img.photobucket.com/albums/v2...k/DSCF0168.jpg

I've heard clogged cat can cause strange problems such as these

Perhaps a pinched/disconnected vac hose? or solenoid problems

I doubt you actually have a leak in your turbos--ic--throttle body. If you had an air leak there, you wouldn't see 1 bar. You would probably get like .4-.5 on both primary and secondary since the leak would affect both.

Please check out the attached file. I tried to figure out from your desc what the boost pattern really is but I'm not sure. So tell me if the guess is right. (You might want a helper to watch the boost gauge for you while you drive to get a better idea of what's happening). Is the 1bar peak in the right place?

The proper boost pattern will help a lot to diagnose if you have a boost leak/problem or simply the boost control needs tuned for the mods installed. If the 1bar peak is correctly represented in my picture, I suspect the latter.
Dave

Wow, you guys are helpful, lads in the UK are a little slower lol

Anyway Dave that pretty much represents whats happening been out in the car today and its behaved the way you have shown on your graph, steady hold now on the 2nd turbo at 0.8 bar just the 1st fails to get anywhere over 0.6 bar. I suspect as the 1st turbo is not pushing full boost, it would explain why the 2nd struggles and then bang hits what it needs.

I am going to do step by step replacement of the intake pipes, change to a 99 Y pipe and then start on the Rats nest of Vac hoses, but maybe i should change the solonoids at the same time? once thats done i am going to purchase a power FC and decate the whole car. Hopefully when im at that point i will have solved it.

Guys thanks for your help, DAve cheers for doing that graph, much appreciated.

Gav

Dave, is this chart accurate? Doesn't 9.5PSI seems quite a bit high when the motor is nearing redline.

Are you on stock precat, cat, and stock exhaust?

A clogged precat may explain why your primary wont get over .6
But if you're on the stock exhaust system, you shouldnt be seeing the 1 bar. If you're on stock ecu, this can be potentially dangerous because you're boosting so high.

Um, isn't the stock pattern 10-8-10 or .69-.55-.69

Some stock cars hold 10psi all the way, others taper off a bit.

I think it's a precontrol adjustment problem. When the precontrol is flowing too much too soon, it takes away from primary boost and overdrives the secondary during the prespool stage - such that at 4500 the momentum of the secondary surging causes that spike. It's not good, that spike. How is your setup currently doing boost control? (Is there still the stock pills in the wastegate/precontrol lines?, could they be accidentally swapped?, could there be a manual or electronic boost controller installed?)

Another thing to check is the wastegate, turbo control, and precontrol actuator rod length. You simply remove the turbo heat shields so you can see the actuator rods meet the hinge arms of the control doors, then remove the e-clip and rod. Each actuator should have about 1-2mm (half the width of the hinge pin) of pre-stretch when fitted over the arm.

De-catting the car adds variables to this boost control issue. I wouldn't do that until you're happy this setup is running right. I agree with the rats nest job - if you can afford all new solenoids, that's great - but IMO only replace the turbo control solenoids with new ones. For the rest, test proper function and replace with good used ones as necessary.

In either case, if this issue is a precontrol issue, it's may not require a full rats nest dig to fix. I'd focus on that alone before moving into the rats nest job or other mods. Run searches to find good info on the stuff I mentioned above - there are threads with pictures, etc. that should walk you thru it.

Dave

Well the things you describe sound very similar but, the car still retains primary cat and also a standard ECU there is no type of boost control. The car is pretty much stock bar the apexi filters and Blitz Nur back box. I plan to go for a straight though once i have the Power FC.

Cheers

Gav

Gav -

Did you ever resolve your boost spike problem? My car has a similar problem. What was your solution?

Thanks

Dave