GTX2867R, FM log mani, 1.8, 8.4cr
 

1.8, iron log FM manifold, GTX2867R, 3in turbo back, pump 93, MS1, Deatchwerks 750cc injectors, LS2 coils, 8.4cr Supertech pistons, Crower rods, Boundary pump, NA8 head ported by Miata2fast, stock valves, Supertech light double springs, stock cams.

The blips in the first run were where it was hitting overboost at about 15.25psi

About 15psi
262whp @ 5810rpm
252tq @ 5050rpm

https://www.miataturbo.net/attachmen...ine=1446468395


https://www.miataturbo.net/attachmen...ine=1446468585

screenshot of spark map?

Nice, thanks. That's about where I am right now with timing & afr on my gt2560r

I don't think I'd call that spark table conservative.

I wouldn't call it conservative either.

Why is the spark table 8x8?

It is an MS1, so smaller fuel and spark tables.

Ha, you're running within a couple degrees as much as I'm running on E85. I would hardly call that very conservative.

Even with 8.4cr and 93 octane? Hmm. What would you expect for the top couple of rows?
There seems to be a consensus brewing.
I seem to recall adding two degrees to the top of the map back a year and a half ago because I felt there was too much heat in the exhaust because of the (I thought) overly retarded timing. I saw a few others running more and felt I could safely add a couple.

Are you using low or high compression pistons with the E85?

IMO the 183 row is really the one that's kinda aggressive, and maybe the 212 by 1 or 2, top row aint that bad.
and y'all have proper fuel and not CA 91oct water, so I don't even think it's that bad.
also the spark is not 8x8, that's the afr target table, unless we're looking at different tables.

...I'm not really impressed with how late that thing comes on though, that's for sure.

I think that is due to the cast manifold. Hustler had some old threads about his 2860 spooling like donkey shit on a begi cast manifold.

Yep, I remember that.

I know it's not apples to apples but at 10:1 and with VVT I was able to get over 200lbft by 3750 rpm on a precision 4828 on a BEGI cast manifold. (195kpa)

FM 9.0:1 Weisco pistons. Nothing crazy.

FWIW I think your spark map is great if it doesn't knock, just noting that's not super conservative.

Me either. It has the .86 hotside but with ball bearings and a billet wheel I expected better.

On my GT3271, I found a lot of spoolage by not running pig rich while it spools. I ran it around 14:1 at 100kPa, 13:1 at 140kPa, etc, tapering to target AFRs when you get to target. That made a very very nice improvement in both driveability and spool. Worth a shot since your posted AFR target table is richer than needed at very low boost.

Great advice if you want to blow your motor up.

Lol. Please give me some notes if you have any to share. I'm winging it carrying the Miata flag in the land of vettes and mustangs.

I didn't say run stoich at full boost. I did what I wrote for a few years and didn't blow an engine up at 140kPa or 100kPa doing it. Det cans and common sense.

I would have thought a bit more fuel in the ramp up section would cause it to still be burning when the exhaust valve opens and therefore expanding in the exhaust manifold. But that's just a preliminary thought since you brought it up. I'll have a cup of coffee and think about it.

I'm actually a little surprised at the top end, 15psi on a turbo that big with a 1.8L and makes the same torque as my 2554R/stock 1.6L/Begi mani/2.5" exh/13psi from 6000 to redline? I am on E85 but I figured the GTX with a 3" exhaust would be flowing a lot more efficiently than a 2554 in the high revs. :dunno:

Yep, that too. It falls off really hard up top, so it's lose/lose

Log begi mani or tubular?

I dont think begi made the s4/s6 for the 1.6

That rich does slow the burn a bit, but it also drops your EGTs which is bad for spoolage. Leaner drives up EGTs and helps spool the turbo.

Example, assuming the dyno wideband is accurate: https://www.miataturbo.net/dynos-tim...5/#post1280722

The "direct pulses" or whatever it's called, cast mani.

which (imo) is still better than the FM in terms of flow, but still lightyears behind proper tubulars

A year later....did this ever get figured out? Im trying to pick my next turbo but these results aren't helping. It took codrus 24 psi and 100 octane to make 340 on the 63mm billet wheel. I still think the bigger gt2871 may be superior to the billet stuff

Yeah, threadsurrection, but..

These numbers are far from impressive, Im about to run a Premium Gasoline NB8a setup with a GTX2871 and if it doesnt destroy this setup ill be so mad.

Dann

Even a standard gt2871 should destroy this. A gtx2863 did destroy this. Thats why i asked if it got figured out because something is up

I haven't changed anything since that dyno run except some reliability mods. The possible restrictions are the FM log mani, the 70 degree bend in the 3in downpipe about 10 inches from the turbine outlet, the 2" hotside intercooler piping, the intercooler, etc. Everyone so far says my timing is good, but pointers are welcome. Is base timing off or maybe a tooth off on a camshaft? I'm not sure.

It's been parked mostly and I've been busy selling a house. But I'd love some ideas.

Cant be the manifold. Miatamike did 400 on a begi cast mani. FM has built 400whp+ stroker motors on their mani. I dont think it flows as good as a proper tubular, but it should be fine for 300-350+

2 inch hotside IC piping shouldn't be a big deal either. Again, FM runs 2 inch and its fine. And the standard size for the turbo outlet is 2 inch

Whats your air filter setup? Maybe choking the big azz turbo?

Still puzzling tho. Im still thinking this is the turbo for my goals but if i struggle to hit even 300whp ill be mad asf

Air filter is of adequate size but is in a poor location. Using NA8 intake manifold and Skunk2 throttle body. 3 inch downpipe is covered in heat shields but I have an old picture from a prior disassembly depicting the sharp turn. It is still many times larger than the turbine outlet so even though it's not ideal I don't know if it could cause a tremendous amount of restriction.

This is the downpipe and manifold (with a different turbo).
https://www.miataturbo.net/attachmen...426_113819.jpg

This is a good depiction of the difference between the turbine outlet size and the 3in pipe:
https://www.miataturbo.net/attachmen...426_132910.jpg

Again, the bend in the downpipe (very old pic, many of the surrounding components have been changed or rerouted):
https://www.miataturbo.net/attachmen...426_113532.jpg

As she sits this morning. Note air filter location far less than ideal.
https://www.miataturbo.net/attachmen...906_074552.jpg

https://www.miataturbo.net/attachmen...906_074531.jpg

Its not the downpipe. the hotside, and I use some silly small intercoolers on dumb builds, its unlikely that.

the cheated radius on the downpipe right at the turbine exit doesnt look like it would promote flow very well but who knows. thats not the gtx2867 is it? looks like a small chinese thing

This is the GTX2867R:
https://www.miataturbo.net/attachmen...906_074531.jpg


This was Chinese 2870:
https://www.miataturbo.net/attachmen...426_113819.jpg

YUP. :eggplant:

not even talking about spool tho. there is no reason the HP should be this low

if i had a turbo that big and shiny and was making as much power as ppl with stock engine and gt2560 id lose sleep at night. not even trying to sound like an ass, just trying to pick my next turbo and i cant have this happen to me...

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

Attachment 183235

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:

http://www.codrus.com/dyno/synergy-O...ynergy-265.png

--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
https://cimg6.ibsrv.net/gimg/www.mia...a4d7959ba1.jpg

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