3" exhaust or reroute
 

I have a T3b turbo, MS3X, LS2 truck coils, and custom intercooler piping on a stock 1.8 engine and I have a little bit of money to spend on the car. I'm trying to decide between changing my crappy 2.5" exhaust with a diy 3" mandrel bent exhaust or a coolant reroute . Right now my cars spools really slow. I'm sure changing the exhaust would improve my spool a good bit. Here is a screenshot of my spool.
Attachment 104350

Just wanted some opinions on if I should go with exhaust or reroute. I will be keeping boost at 8 psi for at least another year and am leaning to the exhaust.

Here is a pic of my engine bay as it sits.


https://www.miataturbo.net/attachmen...ine=1393302099

That's a really really bad datalog.

Maybe it's just me, but i can't see anything from that.

Also, i doubt 2.5" exhaust is slowing your spool that much.

Do you have cooling issues? If not i would advise trying to fix that spool issue. I do doubt that the 2.5" downpipe is causing the issue but im sure a 3" would spool faster and make more power anyways. Tune time is likely what you need.

Brainy wants your spool data.

Post your spool there for comparison.

Is your wastegate adjusted properly?

Boost leak?


We just had a thread almost exactly like this a few week ago.

Are you tapping your gas pedal foot to a song or something?

Where are you getting your M/EBC wastegate signal from? If it's not from directly below that hideous blue 90* coupler off the throttle body, change that first than come back.

I'm running a tial 35mm wastegate and don't believe they have any adjustments except changing springs.

Curly, you are right I had that on one of my to do lists and just forgot it, thanks for the reminder. I will also swap out that terrible 90 with a black one.

If these changes don't improve spool I will perform a leak test on the intercooler piping.

Thanks for the suggestions.

Make sure you have a bit of preload (spring pressure holding the wastegate flapper closed) with that Tial. If it's cracked open at rest, exhaust is bypassing the turbine.

I removed my Tial Bov a couple of months age and need to check and see if the oring got put back on. I will let you guys know if that is my problem. I appreciate all the ideas on what is wrong.

BOV and wastegate actuator are two different things. ??

I understand the difference in a bov and wastegate. I have a tial bov that was removed and I think I'm missing an oring between the flange and bov that may be causing a boost leak.

Also make sure you have the firing ring in your tial gate. Its like a metal o-ring that goes between the flange and the gate, without it you might aswell have the gate open all the time.

I was correct there is no oring on the bov. Could this cause a big enough boost leak to account for my late boost. Guess I will hit eBay up for one tomorrow.

^^^^ This!

Early gate opening symptoms. You'd need to have a MAJOR boost leak to spool that slow, and you would hear it for sure.

You definitely don't need 3" exhaust at 8 psi. I'm running 15-17 PSI (depending on weather) and making ~300 whp through 2.5" exhaust and see no reason to go bigger at this power level. Hell I made 235 whp on 12 psi through the STOCK exhaust.

Thanks for the reply. I didn't think a boost leak would slow my spool this much. I will check the wastegate but I'm pretty sure the firing ring is in there. It never hurts to double check.

Installed new bov flange oring and took the car for a drive. The datalog shows better spool, but after looking at the old logs they show I was only at partial throtlle (50%). Here is a pic of the datalog. This is a 3rd gear pull.
https://www.miataturbo.net/attachmen...ine=1394037224

Do you guys think that this is reasonable spool for my setup. Let me know if you want me to load any other information.

That looks much more reasonable.

Why part throttle? Were you really part throttle or do you need to calibrate your TPS? Being part throttle hurts spool (obviously).

Hornetball you may be correct that my tps calibration was incorrect and it was actually full throttle. I did have my tps wired incorrectly at one point but I'm not sure if I fixed it before or after the previous spool data.

How much spool could I possible gain from changing from a crush bent exhaust to a 3" mandrell bent exhaust?

Why do you keep wanting to spend money on your car when it's not needed?
Fix the tune. It's free, and easy.
Find the problem. Fix the problem.