My 3B to RS2 project

[newsh]

it could be that the 200.000mpg old wastage needs some servicing rather than needing a bigger one.If that wastegate was indeed the problem of it being too small,then why is it that everyone of us using the same turbo,isnt having the same problem so far?...It could be a mixture of things as well and not just one thing.Low backpressure from your exhaust+ years of muck in the wastegate making it actually smaller than it can be...

Logic says though that if there was an issue with the wastegate and this level of turbos,then all I5 engines with bigger garretts should have been using Tials already.I have seen the boost being a problem on a GT35 garrett,not the 3071 or the 3076 so far

Absolutely correct.

[gedu]

Yep, there is always the possibility that original WG is past its due date. Spilt membrane could do that.

Full throttle boost control is one thing, part throttle usually is the hard part. I want my engine to be able to keep that ~1bar boost stable to redline if there comes a need to do it

[A80Avant]

it could be that the 200.000mpg old wastage needs some servicing rather than needing a bigger one.If that wastegate was indeed the problem of it being too small,then why is it that everyone of us using the same turbo,isnt having the same problem so far?...It could be a mixture of things as well and not just one thing.Low backpressure from your exhaust+ years of muck in the wastegate making it actually smaller than it can be...

Logic says though that if there was an issue with the wastegate and this level of turbos,then all I5 engines with bigger garretts should have been using Tials already.I have seen the boost being a problem on a GT35 garrett,not the 3071 or the 3076 so far

[Jamo]

hrmm, with internal wastegate you are begging for problems with small garretts

Stock WG might start putting things into disarray quite easily, as it doesn't flow _that_ much, and if you want to run low pressures, you really have to be able to divert lots of gasses from turbine. Putting back-pressure into exhaust is just "wrong" way to tackle it, get a larger WG that can divert enough gas from turbine

Of course, loudness is also quite tiring, and yes, you almost always get more back pressure when quieting things down.

I agree, I'm sure someone said earlier the wastegate was too small, can't imagine who.........

The wastegate really needs porting, the gasket to gate is shocking there is so much that can be taken off.

I'll take a picture some day if I can.

[gedu]

hrmm, with internal wastegate you are begging for problems with small garretts

Stock WG might start putting things into disarray quite easily, as it doesn't flow _that_ much, and if you want to run low pressures, you really have to be able to divert lots of gasses from turbine. Putting back-pressure into exhaust is just "wrong" way to tackle it, get a larger WG that can divert enough gas from turbine

Of course, loudness is also quite tiring, and yes, you almost always get more back pressure when quieting things down.

[newsh]

Yeah, seems like the guys who run internal wastegates get this all the time, it shouldn't happen to us unless we go GT35 and larger..
My WG is original with over 200,000 miles on it so may not be opening fully, so I think I'm going to try a new wastegate first, I can borrow one , if that doesnt work it might have to be a Tial, unfortunately the prices on 034 seem to have gone up recently, they do a drop in 44mm one IIRC.

[Rusty]

Ah, that's a new one but now I've read it, it makes sense.So if your WG is too small and isn't flowing enough gas to stop the turbo spinning faster then I guess that it's all about path of least resistance. If the WG is more restrictive than the turbine & exhaust assembly then it ain't gonna flow that way. What you need is some exhaust gas that enjoys taking the long wy round, a sort of petrolhead's exhaust gas

Are you going to get a larger WG on there?

[Acidburn]

We need some videos

flyby's etc.

[newsh]

Now that the boost is not creeping I've wound the spring down to give 1.5 Bar boost, these GT turbos spin up bloody quick don't they

[Acidburn]

Sounds interesting and something different as I always thought that it was mostly NA engines that needing the back pressure to help with power.

Still interested in hearing it in person

I used to have loud exhausts etc and they was ok but I have noticed that its ruined my hearing a bit

[newsh]

Did a search on Boost Creep. Lots of stuff out there.

Found this which explains it.

http://www.rx7club.com/showthread.php?t=26389

The best way to deal with creep is to
1) port your wastegate
2) add some restriction to your exhaust.

The creep is present because of too much flow through the turbos despite the wastegate being told by the ECU/boost controller to be 100% open.

You will not have boost creep problems unless you are running a full 3 inch exhaust (DP/MP[with or without resonator]/CB). Adding some restriction such as a hi-flow cat, or a more restrictive catback exhaust, or a restrictor plate in the exhaust flow can help.

A restrictor plate is just a gasket (made of metal) that has a hole that is smaller than the internal diameter of the exhaust piping. For example, having a hole of only 2 inches.

You can place it between the DP/MP, or between the MP/CB. I am not sure of the best location. I ran a plate between the DP and MP. As the gases get further from the exhaust manifold they will cool and become denser. You can also run silencers in your exhaust if you have for example the Apex'i GT or N1, or N1 Duals.

The plates are easy to make if you have the right tools, or you can have them machined by a shop. I had a bunch made up when I just wanted one, but now they are all accounted for.

Hope that helps.

Ulimately, the best thing is to port the wastegates. . But with the plates you can keep the boost down to a reasonable level, (depending on how free flowing your exhaust is, how good your turbos are, and the size of the hole, 10-14 psi [ I tried a bunch of different sizes] but you will need the fuel to compensate for the increased boost.) This is not an issue if you are tuned for 14 psi and run 14 psi max.

The Borla XR-1 is a silencer/resonator. I have it welded in the middle of my MP. It has 3 inch inlet and outlet, is a straight through design, with perforated core, and sound absorbing material inside that is apparently able to withstand the hi temps of rotaries. They are about $125 from summit racing, and my exhaust shop charged about $20 USD to weld it in.

Mike
Last edited by the_saint : 10-18-01 at 09:52 AM.

[newsh]

It is insanely loud at certain rpms even at a tiny throttle opening at 30mph, especially inside the car, my ears seem to start ringing within a minute of driving in traffic. At high speed with the revs above 4k its ok but still loud enough so everybody looks, it sets off car alarms as you drive by, its only a matter of time before I get a pull. Anyway its really very annoying to drive.

Have to report though that I fitted the dB killer this morning and there's a big difference, even without the extra box. A lot of the boom is gone although I'd like it a bit better yet.
Most importantly the overboosting has mostly gone and it will now run mechanical boost up to the redline apart from a small increase of 0.1 or so Bar above 5k. So Doug was right and the extra backpressure has helped the wastegate to work properly which I must say I find really strange..

[Acidburn]

I'll have to try hear this before you put the box in john, tbh it does not sound bad to me tbh.

when are you planning to get this done?

[newsh]

T'would be dangerous

Of course mate, we dont do that sort of thing on here do we