GRM Think-tank: choose me a turbo for a 1.5l engine

Some time off, but considering the idea of turboing the 1.5l in my Mazda2, vs just swapping a 2.5l MZR with an 07-09 Mazda3 5spd(G35M-R). Good for a relatively easy 200 crank horsepower with minor bolt ons and tune.

Part of that is figuring out what to expect from a turbo setup. Bonus is fun turbo spooly whoosh noises

I previously made a VE calculator in Excel for grins, and I've since added a few more tables to estimate airflow under boost. Frankly I think it will slightly underestimate to some degree, because under pressure it should make up for lower VE with atmospheric pressure, but regardless here are the numbers from my car, based on logged data through Mazdaedit:

Something that will actually spool up and not feel terrible at 6psi on stock internals would be great to just get a system together and the hard parts and tuning established. Long term goals would be to build another long block with forged pistons and stronger rods(notice the bore is the same as a B6T Custom rods needed for sure). Pressure could be whatever it needs to be. I frankly don't think more than about 250whp would even be of much use, and honestly that's about what I'm expecting the transmission to break around, if not closer to 200whp. There is another fellow in Greece who's turbo'd one of these, but he broke teeth off of 3rd gear... which I really shouldn't be getting into.

This is for autocross use(SMF), so pretty quick but controllable spool would be ideal. A faster spool can be controlled by a good boost controller/Megasquirt/etc... but if it's like a light switch when the boost hits, then a slightly bigger one probably could have been chosen to give either more potential headroom, or for lower intake charge temps, etc.

It sounds small, but the compressor map looks REALLY good for a Garrett GT2252 for just about anywhere from 6-18psi. FWIW I'd probably choose the 0.67 A/R exhaust housing. GT2252

And then the GT2854R also looks nice. Same with the 2554R. GT2854R

The question is with the estimated limitations of the transmission, is the 2252 not even at risk of being maxed out(tune power down low with TPS based boost control) and I'm over thinking it? Or is something bigger a good idea?

I can read a compressor map and know if something is at least safe(surge line and efficiency-wise), but the turbine maps I know are essentially useless.

I THINK something that gets positive pressure around 3000rpms, and maybe 8-10psi by 4000rpms would be about right for reasonable response without giving up anything up top if trying to push the turbo size... I'm trying to figure out bigger vs smaller turbo, for lower power levels is there a reason to choose one or the other?

Would one or the other be better suited to HPDE use?

FWIW the Mazda2 1.5l is a low revving(100hp at 6000rpm, 98ft-lb at 4000rpms, stock redline of 6200) 4cyl. With the rev limit raised to 7200rpm, there is basically no power above stock redline, it drops kinda quickly... but while N/A it at least makes sense because the 1-2 shift is so badly spaced out.

WWGRMD?

Volvo twin scroll 12T

(biased)

Making an exhaust manifold to suit would be tricky. I wonder how close the bore spacing is on the 1.5 versus the Volvo engine. Volvos are pretty narrow in the spacing.

I sold an Evo VIII manifold/turbo to someone who was putting it on an SR20-engined Sentra. Said the exhaust spacing was just about correct, just needed to drill and tap the head for the Mitsubishi mounting holes.

For less finagling but no twin-scroll goodness, how about a TDI turbo? An early non-VNT model.

In reply to Knurled:

I can't find compressor maps for either of those turbos you mentioned... But I'm thinking the 12t would be too small... Mainly because many Miatas run the TD04h-15G and it's map looks reasonable enough.. Though the 16t is more efficient in my projected P/R vs airflow.

Fabbing a manifold is no big deal so whatever I get I'll build around. Having upgrade options would be nice for down the road and is worth considering when choosing a turbo.

Anyone else?

K04 out of a cx7 should be nice.

flatlander937 wrote: In reply to Knurled: I can't find compressor maps for either of those turbos you mentioned... But I'm thinking the 12t would be too small... Mainly because many Miatas run the TD04h-15G and it's map looks reasonable enough.. Though the 16t is more efficient in my projected P/R vs airflow.

It is good for about 200hp at 14 pounds of boost. Will make 10-11 pounds at ~2500rpm on a 1.9l engine with ease. I haven't turned up the boost past that

You're looking for response, and a fairly low RPM ceiling, with a smallish engine, yes? You're not going to want something very big. Response is more important than ultimate power for everything but dyno racing and dragstrips.

Ko3 off a vw 1.8t, tiny instaspool things that flow well at upper pressures. Friends tuned 1.8t golf with stock turbo pulls VERY well.

Ive got a tdo4hl-15g on a 2.3 and its not exactly the bees knees although it makes 200whp with a crappy flowing head id rather have the ko3 on a small motor

Get 4 tiny baby lawn mower sized turbos and do this. Bonus points if you run ITBs too!

Another one....what about a gt28rs "disco potato". Designed for...1.8l? But it spooled like a muuuuch smaller turbo. I have to imagine theyve fallen off the bleeding edge and become cheap, its at least a 15 year old design.

If you don't mind cutting and welding cast iron (manifold and turbo are cast as one), I've seen these for about $700 bucks. They flow 200 hp stock and insta-spool on a 1.6L Veloster.

http://www.jimellishyundaiparts.com/products/Hyundai/2013/VELOSTER/TURBOCHARGER/8468639/282312B700.html

1.476 L Hayabusa engine would work right?

K03 K04 or hybrid of some sort, you can get take offs from the VW's for cheap. Good for a decently efficient 15psi and too-quick spool on a 1.8. Would be a good choice for a 1.5L with a low redline.

I have a legit Garret GT12 if you want to spool off idle. It will likely run out of steam by 6k but man that mid range should be gnarly.

Stock motor may be an exercise in futility for the cost, but something like the 2252 or 2554 would work well for ~6-8psi (~140-160whp) up to ~12psi (~190whp?)

Unfortunately the EFR6258 is the smallest EFR turbo made (~44lb of flow) but the spool would still be good (built block application, ~15-18lb of boost, ~205-240whp?)

Twin Scroll and Ball bearing are going to make/break a larger (EFR) turbo driveability, especially in autocross. If you're fabbing the manifold it's definitely worth at least exploring twin scroll.

The Mini S turbo cars (2007-11) had a twin scroll that's probably good for ~225whp (at 18psi) on the 1.5L, as it does about that on the 1.6L bmw motor. (friend who owns one says usable boost around 2000rpm, full around 2700)