jaredcolletti

I have an 87 t2 with the mods below (please read first) Engine blew as a result of detonating according to dave atkins (blown apex seal, 4k on engine) correct ne if I am wrong but it probablt occured from leaning out, spiking or over boosting.

So, I need to play it safe now, its getting expensive. I was thinging of replacing the stock airbox over and removing the MBC, the WG is ported already. the walbro isnt rewired or even in yet, I was gonna do it before the engine blew. It has a BOSCH unit installed now.

Please, any help would be appreciated. what can I do to be safe here. I would hate to pull my racing beat full turbo back. I can I keep it and still be safe?


thanks allot guys and sorry if my lack of knowledge out shines my question.

jared

Dan H

Well, we need more info. With the MBC, how much did you crank up the boost (what PSI were you seeing?)

The Walbro fuel pump should have been wired in when you started going more than stock boost levels.

NZConvertible

You've already asked this and gotten good answers.

https://www.rx7club.com/forum/showth...hreadid=200068

ViRuS

You needed bigger injectors and that pump in before you blew the motor, not that safe to run more that 10 psi on the stock fuel system. Need to keep fresh plugs, and wires in there, good ones not cheap ones. Well it seems you did get answers on your other post, (good ones those guys know their stuff) maybe your asking the wrong questions. I have a full turbo back exhaust and stock fuel system, stock turbo and wg. I run 91 octane pump gas. (thats the highest here) I started to detonate once due to my plugs burning out very quickly, and they would burn out fast because of my wires. I know have NGK wires and run fine. I can safely (on my car)run up to 10psi but thats pushing the injectors and pump pretty hard. (Remember that stock boost is set way lower) I have been running 8psi for over 2 years with a little over 30k on my Mazda rebuilt. I think the turbo can only handle 12psi ( I think) Well thats what I think anyway, a good way to keep it safe. Porting the WG was a good move as our gates were not so good. I need an s5 turbo and WG.

1SxyRXy

you need injectors for that fuel pump too dont you?

Barwick

Um.. you want to limit the boost, yank out that stupid MBC and hook the wastegate up straight up. It'll boost to 5 lbs, and if you can't run 13's with only 5 lbs, then you suck as a driver. My car does it just fine and it's much heavier than yours, and has much less mods.

It'll boost to 5 lbs and maybe creep a little, but not anywhere NEAR as much as it's creeping now. I've got a full exhaust and intake and mine doesn't creep hardly at all, most I've ever seen is strangely enough only in 4th gear, and that's 7 psi.

Josepi

Then why don't S5s that boost better than 5psi stock run 13s?

jaredcolletti

oh yeah.

i hit 10.5-11 pretty fast and make the needle dance around with ease

Barwick

Because running 7.5 psi on a stock car isn't the same as running 5 psi with a full exhaust and intake.

jaredcolletti

yeah. I figured I needed to pull the MBC. clean injectors. rewire pump. shoul;d I but stock air box back in there?

Barwick

No, listen..

My car probalbly flows about the same thorugh the (stock) S5 wastegate as yours does through your ported S4 wastegate.

That being said, look at my setup. The DSV does not open on my car for whatever reason, so I have NO boost control other than the wastegate spring. It runs 5 lbs in 1st 2nd and 3rd gears, and goes right to 7 in 4th gear, and doesn't hit 7 in 5th (I suppose unless I'm doing like 140, which I haven't done yet, but who knows..)

Pull your MBC out, and leave just a direct connection between the wastegate and the pressure side. It should run similar to mine without much or any creep.

jaredcolletti

cool...whats the "DSV"
I got ya though

thanks dude.

jared

Dan H

You can do that but a better option is to build a cold air box around the current filter you have now. Just leaving the filter out in the open (with all that engine heat) is not doing any good.

ViRuS

How are you running 5psi with the a full exhaust (by full you mean no cats right?) Do you still have the airbox on.
I know you have a better WG, but I don't think it can dump that much at full throttle. Also I see that your motor is a j-spec, don't those motors have bigger ports than ours? Your engine puts out more power to begin with, thats why you can run a better time with less boost. We need more boost for those times, or a street port. DO you have all the j-spec parts(turbo,ecu,injectors,ect...)

I have a full HKS turbo back and I need a MBC to limit my boost to 8psi. If I run it straight, It shoots up to 9.8-10psi. Even if I ported it, it only comes down to about 8psi I believe(my friends car). Mr. Mazda's car (Mike)runs 13lbs with a ported S4 WG, but then again he has upgraded S5 turbo with turbines from turbonetics...so I dunno. But do you have a pop off valve, or a dump valve? How do you limit your boost to 5psi, isnt that lower than stock? Well anyway looks like you have a good setup there and good times!!

Barwick

a MBC can't limit boost unless it replaces something else (another boost controller) that is setting it higher.

And the J-Spec engines are the same exact thing as the regular engines, except for emissions.

And I don't know how it's only holding 5. But I'm guessing that if I had a MBC and set it to 8, it would creep well past that. And like I said, my car is in the sig, cone intake and full exhaust (yes no cats)

SonicRaT

iTrader: (6)

As Barwick just said, a MBC does NOT limit boost. You want to have better control, port your wastegate more.

chris1234p

I belive he said he has his wastegate wired open, which might keep the boost down that low.

Barwick

definitely not wired open, don't know where you got that.. especially considering if I pull the wastegate line, it runs up WAY past 8.

ViRuS

Even with the WG ported they are to small to dump that much boost with your mods. Well thats what I thought and that might be why you see that creep in your higher gears. At high rpm with my gate fully open it will creep past 8.5psi but that has nothing to do with my MBC, the WG just can dump it fast enough. Maybe I should port it...
Thats strange that your car sits at 5psi most of the time? haha thats good stuff



My WG is not ported. Porting it more would be my 1st port if I did it. And a boost controller is supposed to control your WG. Keep it open longer or close it sooner. How can I control something that I would have nothing to do with, like a bigger hole in my WG. Should I ask it nicely to set my boost at 8psi and hope for the best My MBC works, if I want more then I turn it up, Less goes down, although Less is only about 6.5psi and creeps to 7psi in higher gears...?

I thought they had bigger ports and thats why people got them? The turbo and WG? Waite... do you have a j-spec WG. I am still pretty sure they have bigger ports,but I guess I could be wrong

NZConvertible

Various answers for everybody:

Boost controllers DO NOT LOWER BOOST! Whether they're $10 manual ones or $1000 electronic ones that cannot lower boost, only raise it.

Wiring the wastegate open will not lower boost because over ~5psi it's already fully open. It will make the turbo spool much slower (i.e. much more turbo lag) but it will still creep just as much if the wastegate port is too small.

J-spec motors have identical ports, wastegates and output levels. Apart form some minor details the only difference is less emissions gear. People get them because they're cheap, not because they're better.

The only reliable way to lower boost (apart from adding intake/exhaust restrictions) is to increase flow through the wastegate. Get a turbo shop to fit a bigger flap and port the wastegate out as big as the new flap will allow. This has proven to be very effective at stopping creep. Just porting to the edges of the stock flap isn't enough with 3" exhausts. Another way to improve wastegate flow it with a seperate exhaust pipe for the wastegate. Read this thread for more info.

ViRuS

They lower boost to a certain degree...

As much as my WG will allow. It is true (my car) that I can not lower the boost below 6.5psi due to my mods but I can turn it from the 11psi it would have without the HKS MBC to 8psi. (min of 6.5 with a bit of creep) Other wise it would be going way way way to high

So... they do lower boost...

Jaared

not true.... enouf said.

jaared

ViRuS

These little things are cool...

Jaared

so how do you plan on making the waste gate open sooner with a MBC... its job is to make it open later.

I think some of the external waste gates allow you to plumb a pressure line to both sides of the diphram(sp?) and lets you adjust boost up and down.

But the wastegate we have opens when it sees a preset amount of pressure in the line going to the actuator(sp?).. The MBC holds the pressure in the line back till you get the the desired boost level (stock or higher) then opens the waste gate and diverts some of the exhaust gasses away from the turbo so keep the turbo from making more boost.

So when you figure a way to make the waste gate see more pressure than the engine and open the waste gate sooner than the MBC will never lower boost.

now post more silly smilies and maybe someone will think you are right.

jaared

ViRuS

OK tough guy how you like that one

If you want to be a word tech, ok! If you say so... I dunno why your upset, we were just having a little rx7 talk...what's that you say, we cant to that here...?????? You need to calm down you forum tough guy!

So a boost controller just turns it up? HUh. Word tech guy!! You saying that when I want a little more boost like, oh lets say 11psi, (from my 8psi) that I can't turn it back down? Is that what your saying? So it just goes up and up and I can never set it back to 8psi (Yes from 11psi to 8psi, thats 3 psi less, my math says that would be turning it down) So whats the WG do there? Does it open wider, longer, sooner. Let me know since your so smart and I seem to be wrong all the time. I believe electronic ones have a couple of settings. But according to you, once the high setting is there is no going back...

That was not cool man, but here you go... Thats the best one haha... an your name is spelled funny so