Don't give up on the GTX lineup just because one setup doesn't post dyno numbers you're looking for. People have hit 300whp on a GT2560, no reason at all that you shouldn't expect a GTX2867 to do it. As much as these turbos seem to like high boost sixshooter would be +300whp with a few more psi, it's not like he couldn't get there if he wanted to.

Virtual Dyno results of my last car:

GTX2860, E85, begi cast manifold, stock '99 pistons, forged rods

 

lol ive been watching your utube videos over and over!! i believe these VD results with the 11 second passes on there. what size turbine housing are you using?

Ive been reading compressor maps a little and i think im going with the gtx2871. Wont even be breaking a sweat at 320whp and I could probably see 400whp someday if i get an allofit engine.

my next goal is 340whp on a stock 99 engine with manley rods and e85

 

Haha, thanks.

It's .72 a/r. Special Turbine Housing T25 Inlet, Cast 44mm EWG Port : atpturbo.com

 

dammit. my only choices are .63 or .86 (tial v band)

 

I think the oddly low peak power in the RPM range is a clue as to where to look for the problem.

 

Yes, I'm going to double check cam timing per our conversation. It would explain a lot.

 

it is my understanding that it would shift the power curve one way or the other depending on whether advanced/retarded, and it looks like you have neither the low end grunt nor the top end power.

I'm thinking restriction

 

I made 340 rwhp on a GTX2863, a 2867 is capable of more. Lots of boost and enough octane to run decent amounts of timing. This was with 24 psi of boost, and there's a lot more power there if I had more octane:



--Ian

 

Ill be using e85. I want 330-maybe350whp. I know the gtx2867 can do it, I just don't want to run crazy high boost. I want to be at 330whp around 20psi.

Its tough bc im pretty sure the 67 can do it but i feel like the 71 will be able to do it easier with less tuning and have way more headroom. Plus its only 4mm bigger..which will be like 2 or 300 rpm less spool. Not even a big deal

 

Why do you care what the boost number is? From a reliability standpoint, the motor cares about revs and torque, not about manifold pressure.

330-350 should be quite doable on E85, though.

--Ian

 

Ill be on stock pistons. I don't care about the actual boost number. I just assumed more boost would add more chance for det, wear the rings more, make the turbo less efficient, etc. I think the power would be more reliable at a little less boost pressure? Or am i retarded?

 

you need to read moar young grasshopper

 

I think it's restriction too. But nobody seems to agree with me that it's that awful downpipe. Could be the cast mani too but I think it is at a minimum a combination of the two.

 

oh the downpipe is junk. but while the shape is terrible, it seems to still have at least 2.5" worth of girth so I dunno if it's choking at only 250

 

Yes, more boost will add greater likelihood for detonation, which is why I specified adequate octane. E85 will make it a non-issue, though. Rings don't wear from boost pressure, and the turbo efficiency is an attribute of the turbo itself. One of the things that makes the GTX turbos special is a redesigned compressor section that retains efficiency at much higher pressure ratios than the equivalent GT turbos, which means you can run them at higher boost without getting sky-high intake temperatures.

Generally speaking, torque is proportional to MAP times displacement. Engine breathing mods will move the torque peak further up or down the RPM band, but they won't really change the peak value by all that much. Since power == torque * RPM, this means that you get more power either by adding more torque (and with fixed displacement this means more boost) or with more revs. More revs means cams, head work, better-flowing manifolds, etc. The parts and knowledge for building a Miata motor to take boost are generally cheaper, more available, and easier to DIY than for revs.

From what I've read (never tried it myself), stock pistons can be used for higher boost better than stock rods can, but will reduce your margin for safety in detonation.

--Ian

 

Catalytic converter?

--Ian

 

Check to make sure the throttle body is opening up all the way when mashing the pedal before doing anything else.

 

Can you help me with compressor maps? Does the map tell me how the pressure ratio effects the airflow? If I need 40 lb/min for 340whp, how do I know what pressure ratio that will be at?

If i was at 22psi (2.5 pressure ratio) flowing the 40 lb/min, this turbo would be most efficient and have plenty of headroom

 

Please start your own thread, and let us talk about how to help Sixshooter.

 

this thread was dead. i revived it to try to pick my next turbo. you couldve been helping him for the past year..but okay