porsche2fst4you

OK...I am having my waste gate pipe redone to 2 1/4 but I dont think its going to completely cure the problem here. Anyone ever heard of a boost compensator? One of the kids at the exhaust shop was telling me they use this for the rice burners. Anyone out here had these problems and found a fix before they trashed a motor? I cant ever put it to the floor. If I do it only lasts a few seconds and have to constantly watch the boost gauge...in other words...its no fun. On the gas off the gas or halfway in the gas. Car should be producing well over 600 hp but the boost issue has to be resolved.
Stock waste gate on an 88' 930 3.4l efi with a garrett 64mm.
T. Charlesworth did the internals, race valves, plasma coats, balanced..et..Pat Williams (genious) did the EFI..the damn thing just makes too much power!
Kudo's to these two guys.

Y65MPH

Do you run a boost controller? I run a similar engine setup but with a larger turbo. I run 1.25 bar on pump. Changing the size of your dump pipe is not going to do squat.

markaria1

Once larger turbos/big power comes into play, most guys need a larger wastegate or possibly even a dual wastegate setup (at least with the "rice burners"). An interesting subject is that most wastegate pipes are almost an afterthought to the header/turbo exhaust flow path on street cars, whereas with many full out race cars, the exhaust gasses are routed much more directly to the wastegate(s). One would think it shouldnt matter, but once a lot of air (and therefore exhaust)is being moved you want as large and direct of a wastegate opening as possible in order to regulate boost with consistency. Furthermore, if you were to plot boost pressure on a graph during a dyno run you would see that a turbo car will actually overshoot its max boostpressure for a short time until the wastegate can "react" and actually regulate the boost to the intended spring pressure. Of course if the wastegate and related piping is not large enough it may never be able to bleed off enough exhaust gas to fix the overboost problem and voila "boost creep/spikes" can occur. Good luck on your setup... it sounds like fun!


btw, if you are running a boost controller take it out of the equation and try to run the car off of the wastegate spring... if you dont get boost creep/spikes then your boost controller is the problem. If it spikes off the wastegate spring then I would question your wastegate setup. As for a "boost compensator" I have never heard of such a device and I've been into turbo rice burners for a long time

A930Rocket

Are you getting the pipe off the wastegate enlarged or the pipe from the collector to the wastegate enlarged? A lot of overboost is created by built up pressure when the exhaust gasses can't get to the wastegate. This became more obvious with the quicker/better flowing turbos a few years ago.

porsche2fst4you

No boost controller, just a 1. bar spring in the OEM waste gate. I was told to get the pipe cut at the inlet flange and made bigger then reduce it down to the original pipe size of 2 in'

porsche2fst4you

Do you run a boost controller? I run a similar engine setup but with a larger turbo. I run 1.25 bar on pump. Changing the size of your dump pipe is not going to do squat.


So how did you do your set up? Just a boost controller? And how are you getting away with 1.25 bar? I was told by Pat that if I let it boost over 1 bar I would burn it up...

DWalker

Is there anyway you can post pics of your setup? Its hard to give recommendations blind.

kens911

I would stay away from a boost controller. I bought mine cheap from someone here in this board. he got rid of it cause a hose blew off and overboosted and toasted his engine. I ran it fine for about a year then one day at the track it just started overboosting. I think the filters must have been clogged. well a new set of pistons and cylinders later i'm sticking with just a spring. good news is now it's a 3.4 lol I want to be clear he was totally honest with me about why his engine blew and stupid me thought well nothing like that can happen to me.

DWalker

I will respectfully dis-agree, I have had nothing but great success with the boost controllers I have used, and I use them on different cars just about everyday. 90% of my business revolves around turbocharged cars from one platform or the other, so we get to see quite a variety of cars and issues.

One thing I have consistently found is that most EBC (elecrtonic boost controller) issues are directly related to installation including improper setup. Many shops will install a boost controller and not really understand what it does or does not do and then cannot explain it to the customer, who ends up not really knowing anything about how to properly control boost in thier car. I have (multiple times) seen customers sold the most expensive boost controller on the shelf, packed with features they will never use, and so overly comlicated they never understand it and cannot adjust it properly at all.

MBC's are better, but many of the ones raved about on internet forums are barely adequate and only work well in specific applications.

There is a fair amount of myths and "wrong thinking" out there about wastegates, boost control, etc. get propogated and fostered into accepted facts. Its a shame and it hurts the guys out there just loking for answers, so one must be careful.

I still really cannot help the OP without more information and pictures of his WG setup. I can only offer the following at this point-

Generically speaking you cannot lower the boost below what your WG spring is rated at. It is usually a better idea to use a spring rated lower than your target and then use a boost controller to regulate the boost pressure. For example, on my turbo Eclipse I used a 14lb (1bar) spring and used my BC to hold my target boost of 24psi. There are some other things to consider of course, like WG size, exhaust flow routing, etc. that will effect crack pressure etc. and will effect how your setup will work.

The first thing I would do honestly is to check the WG for function off the car, making sure the valve is opening completely and is not sticking etc.. Do not assume it is working properly, even if new.

You can feel free to call me and I will be glad to walk you through some other things to have a look at-
720-212-5838

Y65MPH

My engine was built by Protosport is has titanium rods and springs, flame ringed, block is tailed and pinned, massive injectors wih a custom cam, MAF etc.. It also has an 8000 RPM redline. So it is more radical than yours. But controling a modified engine with a waste gate spring is very foolish. You will always get boost creep with the spring. Put in an electronic boost controller and you will have no problems. Plus your AFR's must we way out of wack. As DWalker said, I run a .8 bar spring with my EBC set to 1.25 bar on low boost and 1.5 bar on high (race gas).

On C16 I can run 1.7 bar.

kens911

mine was a .8 bar spring and the ebc was set to 1.0 bar. worked great till it stopped. I talked to one of guys at imagine before they closed and they said they just go with a spring since it's more reliable.

sprbxr

What headers are you using? One of the big problems with all of the mass produced aftermarket headers is the wastegate circuit is too small and more importantly the angle of the junction of the wastegate circuit to the collector is all wrong. the WG circuit meets the collector at a 90 dgree angle. I had constant overboost problems with my old setup until I change the angle and size of the wastegate circuit. I still used the stock wastegate after modding the headers. CAn you post a pic of your header?

Mondragon

Hi Guys,
i had the same overboost problem. i am running a Garrett GT35R with a Tial 46mm WG. all controlled by an Autronic SM4 with EBC. i was told all sorts of crap about what the problem could be. it all boiled down to a poor selection of headers i purchased from Schnell. the issue with the headers was that the junction where the waste gate pipe connects to the collector was badley welded partly blocking the aperture of the port. we cut the pipe off, ground out the hole shortened the pipe and refitted the WG. the over boost problem was cured.
if you have bought your headers from Schnell you may want to look and see if the port is partialy blocked. mine was about 50% very disappointing and costly to fix.
i hope you can resolve your issue. as the driving at full boost 1.2 Bar i a lot of fun.
Alex

kens911

I have the gsf headers. They were working fine.I did check the waste gate tube when I installed the headers because I had heard of what you described before with several different brands of headers. When the ebc was working correctly it held boost at exactly 1 bar but then it started acting up during my second run at Sebring after that it was an intermittent problem. I think it was clogged filters on the ports for the ebc but doesnt matter it had already toasted the rings and one of the pistons. Went back to just a spring always opens on time every time. It's quite the fog machine at the moment though when the waste gate opens I got oil in there when I rebuilt the motor last time and it hasnt all burned out of the waste gate tube yet. Getting better though.

JBL930

If you are on CIS then a manual boost controller (simple boost T) will suffice, you're no doubt sticking to one boost level anyway. They are a simple mechanical device so there will be no problem with reliability