2018 GTI SE: How would you mod with $5k? $10k? $15k?

[scrllock]

360whp is absolutely safe, and every 10hp you go up from there you’re just trading reliability for HP.

Sure you “can” make 400 on a is38, but it’s an unnecessarily dangerous way to do it with so many better options out there to fit that bill safely.


I won’t go on record saying EQT or anyone else’s is38+ is “better” than OEM.

If I had to guess 12-15 different companies have thrown their hat in that ring & almost all of them discontinued or folded their business entirely in the last seven years chasing that “new, bigger, better, BEST is38”.

I definitely agree that the oem+ IS38 stuff is effectively snake oil. I didn't trust the cheap stuff like EQT's "IS38+" (which doesn't use genuine IS38 housings), so I had my stock unit rebuilt with a nicer ball bearing setup. Figured this was above and beyond nearly everything else on the market. Was burning oil within 400 miles. On an FCP IS38 now, running a bit less PSI, but it's headache-free so far.

The hp number isn't important tho, it's turbine shaft speed. Avoid high boost at high rpm.

Thanks @GTI Jake -- I'm sure you're likely tired of repeating the same information, the thrust bearing thing gives some better information. I'm thinking that S2 IS38 power is fine for me

My is38 is EQT custom tuned for 93 on my 2019 GTI.

Keep your boost to 25-26psi and taper it down up top. Unfortunately EQT's tuning strategy is based around the marketability of PSI, and they're on record saying that 26psi just doesn't feel fast.

 

[tigeo]

I definitely agree that the oem+ IS38 stuff is effectively snake oil. I didn't trust the cheap stuff like EQT's "IS38+" (which doesn't use genuine IS38 housings), so I had my stock unit rebuilt with a nicer ball bearing setup. Figured this was above and beyond nearly everything else on the market. Was burning oil within 400 miles. On an FCP IS38 now, running a bit less PSI, but it's headache-free so far.

The hp number isn't important tho, it's turbine shaft speed. Avoid high boost at high rpm.


Keep your boost to 25-26psi and taper it down up top. Unfortunately EQT's tuning strategy is based around the marketability of PSI, and they're on record saying that 26psi just doesn't feel fast.

You have folks that talk about boost as the single metric to define their tune..it's funny.

 

[GTI Jake]

At what mileage do you consider an IHI is38 to be at the “end of its life?” My is38 is EQT custom tuned for 93 on my 2019 GTI.

I’d much rather replace a tired turbo, than have it blow and shoot tiny pieces of metal through my IC and have to deal with that headache/anxiety of the debris making it to the motor. In my experience though, turbos don’t give much of a heads up before they grenade themselves.

OEM should go 100k tuned conservatively, but the thrust bearing issue if it’s going for broke can happen in one pull (inadequate thrust bearings allow the turbine wheel to hit the housing, which breaks the shaft).

I definitely agree that the oem+ IS38 stuff is effectively snake oil. I didn't trust the cheap stuff like EQT's "IS38+" (which doesn't use genuine IS38 housings), so I had my stock unit rebuilt with a nicer ball bearing setup. Figured this was above and beyond nearly everything else on the market. Was burning oil within 400 miles. On an FCP IS38 now, running a bit less PSI, but it's headache-free so far.

The hp number isn't important tho, it's turbine shaft speed. Avoid high boost at high rpm.


Keep your boost to 25-26psi and taper it down up top. Unfortunately EQT's tuning strategy is based around the marketability of PSI, and they're on record saying that 26psi just doesn't feel fast.

Without an actual shaft speed sensor & these cars being tuned on a requested torque basis it’s easier to claim a safe 360whp IMO.

I totally agree the closer to 30psi you get the more dangerous it is for a is38, but most guys don’t have a real accurate boost gauge and weather conditions come into play for how much boost it’ll take to meet the TQ request.

 

[EpicTech]

OEM should go 100k tuned conservatively, but the thrust bearing issue if it’s going for broke can happen in one pull (inadequate thrust bearings allow the turbine wheel to hit the housing, which breaks the shaft).



Without an actual shaft speed sensor & these cars being tuned on a requested torque basis it’s easier to claim a safe 360whp IMO.

I totally agree the closer to 30psi you get the more dangerous it is for a is38, but most guys don’t have a real accurate boost gauge and weather conditions come into play for how much boost it’ll take to meet the TQ request.

I agree with that, yall should look at my 100k miles OEM IS20 tuned at Stage 2 by Uni, it still looks good and has zero shaft play... incredible.

 

[tigeo]

I agree with that, yall should look at my 100k miles OEM IS20 tuned at Stage 2 by Uni, it still looks good and has zero shaft play... incredible.

I'll be at 100K this year with my OEM IS38 Uni tuned Sportwagen, I would expect the same.

 

[GTI Jake]

My is20 had 94k APR tuned miles, great condition when I pulled it.

Originally I was suspicious it was leaking a little oil before pulling it because the first cold start of the day id get a little blue puff of smoke.

Turns out it’s most likely valve guides, since nothing changed there with the new is38.

Which brings us to the next rabbit hole

Note: I haven’t done this nor and I recommending it, but when in Rome & have access to a cheap spare head…

 

[wascally wabbitt]

My is20 had 94k APR tuned miles, great condition when I pulled it.

Originally I was suspicious it was leaking a little oil before pulling it because the first cold start of the day id get a little blue puff of smoke.

Turns out it’s most likely valve guides, since nothing changed there with the new is38.

Which brings us to the next rabbit hole View attachment 276897

Note: I haven’t done this nor and I recommending it, but when in Rome & have access to a cheap spare head…

Is this showing biggification of the air intake valve holes*?
Are the intake holes considered as much of a bottleneck as the exhaust holes* in the gen 3 EA888 head?

*Idk the terminology, are those holes called valve seats?

 

[Diggs24]

Not a restriction on any stock sized turbo, no.

 

[PerceivedShift]

My is20 had 94k APR tuned miles, great condition when I pulled it.

Originally I was suspicious it was leaking a little oil before pulling it because the first cold start of the day id get a little blue puff of smoke.

Turns out it’s most likely valve guides, since nothing changed there with the new is38.

Which brings us to the next rabbit hole View attachment 276897

Note: I haven’t done this nor and I recommending it, but when in Rome & have access to a cheap spare head…

Has Thomas shown many dyno graphs? His ported heads are a dream. Take those two photos with a grain of salt though, as they were taken with two vastly different focal lengths, the stock head is shot with a wide angle with makes the ports appear smaller.

Also, I'll be pulling the head off my ITR swapped integra soon and put eyes on its ported and polished head for the first time. Needs new valve seals. Maybe on day I'll find a cheap ea.888 gen 3 engine I can build.

 

[Daks]

My is20 had 94k APR tuned miles, great condition when I pulled it.

Originally I was suspicious it was leaking a little oil before pulling it because the first cold start of the day id get a little blue puff of smoke.

Turns out it’s most likely valve guides, since nothing changed there with the new is38.

Which brings us to the next rabbit hole View attachment 276897

Note: I haven’t done this nor and I recommending it, but when in Rome & have access to a cheap spare head…

Would make sense if you go big black turbo, but even with decent sized hybrids, i don't think the gain would be worthwhile?

 

[GTI Jake]

Did anyone read what I wrote? Lol

Edit, nvm I didn’t write it there I guess. Idk it’s been a long day. But I’m only even considering porting the spare head if it’s already going to him for valve seats and guides (depending on pricing of course).