I have an '87 TII that is completely stock except for a 3" downpipe and an exhaust.

I can drive and build boost normally through 1st gear, but 2nd-5th when hitting boost the car surges and back fires.

Is this boost spike? How can I remedy this? This is my first turbo car so I'm learning as I go.

 

Factory boost cut and remedies explained. Lots of good info on this site for turbo cars. http://www.fc3spro.com/TECH/FAQ/fuelcut.html
You need to monitor your actual boost pressure with an aftermarket gauge and make sure your fuel system can support it. You will probably need to port your wastegate to prevent the boost creep. Running too much boost with too little fuel will damage the motor.

 

U didnt had backfire. If so, some intake parts would be gone by now...

On a S5 model the max boost is 0.7 bar. Any higher and the injectors cannot inject more fuel and the engine will run lean. Above 0.7 bar u will get a fuel cut so the boost cant get any higher.

When u remove all the stock silencers and kat, the turbo will be able to go above 0.7 bar.

Im not sure if this is the same with the S4, but porting your wastegate is a solution. Other solution is to modify your fuel system and or program.


I have a ported waste gate and so far i have only had on fuel cut. Now busy to upgrade the fuel system.

 

FC's backfire all the time. Exhaust gasses igniting in the exhaust system, often resulting in flames shooting out the tail pipe... has nothing to do with the intake.

I believe you are thinking of NITROUS backfire, in which case yes, there would be intake parts destroyed. But I don't think OP here is running nitrous.

OP:
Yes you are probably hitting fuel cut. Freeing up the exhaust like it seems you have overwhelms the puny excuse for a wastegate on the s4 turbo. Get an aftermarket boost gauge so you can see exactly what you're boosting, doesn't need to be a $200 one (I lilke the ones with peak/warn features, like prosport) and pull the turbo to port the wastegate. RXSpeed16 posted a good link on how to do this.

 

Fuel cut due to over boosting. This happens all the same with unported wastegates and large, freeflowing exhaust. The FC3Spro page has some info on porting the wastegate in the tech section.

And before anyone says it... Whatever you do, don't put an FCD in as a "fix". That would allow excessive boost pressure to build, and eventually blow the engine.

 

Thanks guys!

No, no nitrous here.

So switching to an s5 manifold and turbo would also resolve my situation, correct? I figure if I need to start removing things I might as well upgrade...

Besides an A/f and boost guage, what else should I be looking into purchasing?

 

While the s5 manifold and turbo are indeed an upgrade, you should still consider porting the wastegate necessary.

As far as stuff to buy... depends on what you want. Want to run more boost? want a pimped out interior? want a new computer? etc....

 

Haha. Touche Scrims...

I'm wanting mid 200's to the wheels.

I'm mainly looking at suspension at the moment, Tokico Blues aren't doing it for me.

I'm going to continue digging back through the forum and soaking up some information, thanks for the help.

 

To set you in the right direction, you could make 250 easily. Will need upgraded fuel pump, bigger secondaries, a way to control fuel (search SAFC and Rtek), and a way to control boost. Keep in mind this is not a comprehensive list. There are about 200 different ways to get to your goals, so I shan't dictate one specific one to you.

Suspension is all greek to me still :P I'm content with my Tokico Blues

I think this is the first time in a long time I've heard someone going to search and read on the forums without being told 5 times by other members, so kudos to you, and good luck.

 

Hey guys, trying to recycle my thread here as to not clutter the board...

I was quoted $200 to have my wastegate ported by a local performance shop. That seems relatively high from what I've been reading on fc3spro.

Before you guys say it, I do want to do the work myself, but I have no down time nor can I weld.

Does the price seem reasonable? Hell, I could get an s5 turbo for nearly that...

 

Jeez thats kind of lame for something you can do yourself..

 

I understand what you mean J-Rat, but I don't really have the time to sit down and port the waste gate, polish it, cut a relief and weld on a larger door. My schedule consists of work, and occasionally sleep and food. lol

 

So an FCD (FCE, whatever) isn'r a good idea?

I thought that was the standard way to defeat that problem (HA!). My csr hsd one in it, ehrn I hot it, but haven't really put much thought into it.

 

Well a FCD will stop your car from cutting fuel to the rear rotor, but it's not going to stop it from over boosting, and if you overboost without proper fuel, then pop goes the engine. Basically a FCD allows you to pretend the problem doesn't exist, right up to the point where you blow the motor.

PS: re-read your posts before posting.

 

Gotcha. As I said, my car has one, but didn't think I really needed it, given that it wasn't modded beyond the scope of realistically stock, anyway.

Yeah, I saw that when I came back, to check on replies, but couldn't edit; ergo I didn't worry about amending it.