Hello there,
so, I'm looking for any data for G25-550/660 on miata engine, especially 2.5L. I'm building two engines for high power application and I'm trying to decide if 550 will spool fast enough on 1.8 VVT, and if I should go for 550 or 660 for 2.5L NC.
Thanks!

 

I've been in the same boat for a long time. Only reputable information I've been able to gather that is somewhat applicable to us is this page/video using an SR20. Outside of that Greg Peters from car passion channel just recently helped tune RileySlides built KA24 running a 550. He made ~450whp on ethanol. I commented on Greg's post on Insta and asked about what it'd make on pump and he doesn't think the 550 can make 400whp on pump gas. I didn't see any spool data, but you might be able to dm either of them on instagram. Greg's post is in his last 10-15 on instagram as of right now so it shouldn't be to hard for you to find. Lastly there was one person (Nbboy_) who claimed to have the g25-550 on their miata, but due to tuning complications never got to post some data for us. Heres what he said:
If only shuiend could post some data from his pulsar turbo...

 

Just had mine mapped today with a G25-550, the graph is flywheel HP so knock off around 30hp for wheel HP.

Two maps shown - the lower one is 0.8bar and the higher one 1.1bar. Tuner said it was flowing great and has huge potential to go a lot higher. A video of the run is here https://fb.watch/ll8HdZeX6s/

 

Which A/R are u using?

 

I am a little surprised on that spool, I was expecting it to come on a little (or a lot) earlier -- are these .49 ar?

 

Not sure on the A/R I'll need to check with the builder.

 

Can we get more details on this build; looks like a BP in the video? A BP with 300whp at 0.8bar/11.6psi on something that spools before 4krpm is thought provoking.

 

Sure -
re-bored to 1.9l, CP Pistons, Manley Rods, ARP studs.
VVT block, Euro flat top intake, Ported & polished 99 head, Supertech intake/exhaust valves & valve springs, Catcam turbo cam & pulleys, ATI damper.
Walton exhaust manifold with Turbosmart 45 external wastegate to a custom 3-inch exhaust.

I just gave an outline spec the place that built the engine (a forged G25-550 build, capable of 450hp but initially detuned to 350hp) and don't yet have all the lower level detail of exactly what parts they fitted. I am picking the car up from the builder next week, where I hope to have all the exact part specifications they fitted.

 

@gianic can chime in for data on a 2.5L

 

That is very good power for just 17psi.
But an estimated 200wtq at 3700 isn't. Even my nonVVT GTX2860 gen2 .63 is ~500rpms quicker.

 

Dont have numbers yet . But it seems capable of around 400hp@1bar .
Full boost cones at 3k and pulls hard from 2k

 

That sounds awesome, which A/R?

 

I don’t have a clue ! It was installed on a 1.8 before and it spooled a bit high .Like a 2871 maybe

 

A/R should be stamped on the turbine housing, I would very very appreciate if you could check it as I'm not sure which A/R should I choose..

 

Shoot 4F on DD rollers is usually an 18% factor going from wheels to engine hp estimation, so 362hp fly estimation probably recorded 307hp wheel. DD wheel figures can feel cruel.

 

henorek, I still haven't got the car yet but will post probably next week when I pick it up.

 

40c degrees
0,4bar 310hp
0,9 382

 

A/R = 0.72

 

Any pics of the manifold? Interesting setup! The Walton tubulars look nice, though am always concerned with longevity vs cast.

Also, any particular reason for only going to 6300rpm? Power is still climbing!

Could you please take a log in the 1:1 gear from full throttle at say 2000rpm until the boost levels out? The dyno ramp seemed fairly quick so it's tricky to compare to other turbos.

Which gearbox are you running? 350ftlb is a lot!

 

Sorry but only this for now - It was a work of art before fitting, I think the website has an image of an unfitted one. They have a lifetime guarantee and look top notch quality so time will tell.

Regards rpm - the limit is 7300, for some reason the scale isn't correct on the graph. It's back to fine tune the map in around a month I'll try and get a better plot then.

Running a 6-speed with 3.6 diff. Trying to be mechanically sympathetic and not smash gears or doing 0-60's, but yes that is a weak point. Maybe a bmw box swap when funds allow, I am not to fussed on the 6-speed, the 5/6 gate isn't the smoothest (at least on mine).


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