New 4 inch exhaust. awesome, except for fuel cut. LOL

[ArmandoP]

Pics below. and More pics on page 2.

So, I got tired of my dinky not even as good as stock exhaust that came with my 89 when I bought it, so I had MDC Motorsports make me a custom 4 inch downpipe back exhaust. Im quite happy with it. The sound is incredible, especially with the BIC DDP.
Heres a quick before and after synopsis with the only change being the new exhaust. First of all, Extra thanks to Jon and Jeff for their help with getting this done and Jon, Ive got to say man, your welds do look damn nice.
Before:
decent midrange power but the engine would fall flat on its face at 5k rpm as evidenced by my dyno pull at the Dayton meet. (and I do mean flat on its face)
Boost would never hit over 6psi without a boost controller. With a boost controller it would hit 12, then fall off to about 7-8psi. Needless to say, no top end whatsoever.
I would normally see full boost by about 3k rpm.

After:
NO boost controller the car now hits 11psi in second and third and taps 12psi in fourth.
I hit boost cut in second, third fourth and fifth gears... WITH NO BOOST CONTROLLER!
I feel no loss in low and midrange power, however, the car now pulls like a bat out of hell starting at 4k rpm. boost cut stops the fun at 4500 and continues to stop the fun if I keep it at full throttle.

My goal is to put the thing on the dyno for another pull to verify my gut feeling that the exhaust is good for about 30-40 horses on the top end, but I cant really do that with the car bouncing off of boost cut constantly.
Is there any way to raise that cut? I know from my MR2 days we used a zener diode to raise it. I would rather not run a lex and 550's just yet as I want to see what the exhaust is really worth power wise and the lex and 550's would skew that number.

Over all Ive accomplished my goal, to increase efficiency to the point where the turbo itself becomes the next bottleneck.

Mod list if it helps with the advice:
stock CT26, no boost controller, K&N FIPK, BIC DDP, MDC Custom 4 inch DP back exhaust, ARP headstuds, Trust Metal HG, aluminum intercooler pipes, Tial BOV, Electric Fan conversion, EGR removed, 7MGE Cams.

 

[ArmandoP]

attachments

 

[bluemkiii]

You can use an fcd(fuel cut defencer) but I wouldn't recommend it because you can do some serious damage with it.

 

[ArmandoP]

I would like to raise but preferrably not eliminate it.

 

[bountykilla0118]

I am at 14psi ...... u can do a free mod such as a hole in the accordian hose or do it the "proper" way by either going with the lex afm, maft, or map sensor.

 

[OfnaRcR4]

I'm just wondering what kind of numbers you got on your last run.

 

[ArmandoP]

I'm just wondering what kind of numbers you got on your last run.

From my dyno pulls in June:
no boost controller - 6psi across the board: 182.2rwhp, 199.85 lb/ft
With boost controller set to 12, falling off to 8 by 5krpm: 205.1 rwhp, 249 lb/ft.

I hate to even post those numbers because they are so crappy, but its amazing to me how bad the stock exhaust actually is.Im dying to get it back on a dyno and get the new numbers, but its a waste of money if its hitting fuel cut like it is.

 

[ArmandoP]

Hey Boostlee, could you post the pictures from the fabbing of the exhaust?

 

[rumptis]

Looking good Armando!

I'm really surprised you are boosting that much with just exhaust.

Have you shimmed your wastegate?

 

[ArmandoP]

Looking good Armando!

I'm really surprised you are boosting that much with just exhaust.

Have you shimmed your wastegate?

Nope, no shimming. That mod list above is complete.
When I got the car back it was hitting fuel cut in every gear. I kept turning the boost controller back and eventually took it off. I dont know if we lucked out and got the length and transitions perfectly or what, but I am amazed at the difference.

 

[mkIIIman089]

Sounds just like how mine reacted at that stage.

I would still check for boost leaks, just to be certain.

 

[MDCmotorsports]

Armondo:

Thanks for the business, and thanks the kind words on the welds. Welding on aluminized mild steel is a real PITA to even get them to look decent.

Im still thinking you have an unknown boost leak some where. When Jeff was taking her home to you, he was so rich that at times when he would decel, YOU COULDN'T SEE THE BACK END OF THE CAR THROUGH THE DIESEL.

Not to mention he did shoot a 5 FOOT F'UGGIN FLAME OUT THE BACK!

I say fix the horrible rich/boost leak issue and I think your fuel cut problem will disappear.

 

[ArmandoP]

Armondo:

Thanks for the business, and thanks the kind words on the welds. Welding on aluminized mild steel is a real PITA to even get them to look decent.

Im still thinking you have an unknown boost leak some where. When Jeff was taking her home to you, he was so rich that at times when he would decel, YOU COULDN'T SEE THE BACK END OF THE CAR THROUGH THE DIESEL.

Not to mention he did shoot a 5 FOOT F'UGGIN FLAME OUT THE BACK!

I say fix the horrible rich/boost leak issue and I think your fuel cut problem will disappear.

Well, I have replaced all of the intercooler piping and the majority of the vacuum lines and it drives identically to how it did before doing that as far as how rich it is. The turbo seals are also starting to go so that is part fo the smoke as well. It is running extremely rich, but I am almost convinced thats a fuel pump/pressure issue. I have some time today to play with it, so Ill get out there and inspect all the coupers again just to be sure. Ill let you know what I find.
Still if it did have a boostleak it would probably not be spooling as quickly and I doubt if it would be hitting 11psi at the manifold without a boost controller.
I'll spend the afternoon playing with it, cause it sure would be fun if it didnt constantly slam off of fuel cut.

 

[ArmandoP]

p.s. 5 foot flames are cool.

 

[MDCmotorsports]

Bypass that J tube and see what happens.

 

[jonstew]

Look'n good, get that fuel cut fixed and that new turbo on there so we can see how she fares against the All-Trac (by the time I get it back your car should be fully built at the rate it's currently going).

 

[Boost Lee]

p.s. 5 foot flames are cool.

:biglaugh: Killin' me, Armando! :icon_bigg

Yes, I meant to shoot you the pictures beforehand, but while the threads here, I'll take advantage of it.

Thanks again for being patient with us...and other than your mysteriously rich running car, I'm glad that you're happy with it! It sounds absolutely amazing in person. :love:

I won't even bother to post a video of the car because in all of my videos I recorded, it just crackles and pops the microphone in my camera because it's so deeply toned. :naughty: It's hands down the loudest and raspiest sounding full exhaust MKIII Supra I've ever heard. :icon_razz

Picture time!

 

[Boost Lee]

A few more!

 

[bountykilla0118]

Price tag?

 

[ArmandoP]

Bypass that J tube and see what happens.

I guess thats the next step.
I just took the entire charge pipe set off the car and inspected everything. Then I remounted and installed the titanium 3000 pipe that I got from Speed-Source and 3 new silicon couplers. Still doing it.
Fuel cut in 2nd, third and fourth. Right at about 4200rpm.

Im not at liberty to discuss the price, but it was WELL worth it.

Anyone else got any ideas? or is this normal on the MKIII when you really free up the intake and exhaust?

Armando