Hi guys. I need your knowledge and opinions on a turbo upgrade. I am looking forward for a better turbo replacement since my current turbo is old school and i believe is worth having something more modern in my baby. At the moment my gt4088 hit 430whp at 1.3 bar and 470whp at 1.5 bar. The power is instant with very best power curve. Fresh rebuild 13b rew engine with large intake and exhaust ports and ra black super seals. I am using hks short t4 devided with 60mm trust 4bolt wg and 46mm greddy bov on custom vmount setup . Which do you think will be a better replacement regarding better spool with higher hp evel at lower boost and more safe (breathe better) for my engine between g35 g40 efr series. I am looking for psr g40 900 t4 devided with 1.06 ar at the moment but i am open for suggestions and i really need you opinions on this. Thanks

 

since you are using your FD for the actual purpose it was built (road racing), dealing w cumulative heat is job one. close behind is being able to have a linear immediate response out of the corners.

Garrett wins on both counts and the focus is on the hotside. i owned and tested an EFR9180 and currently run a Garrett G40-1150.

wow, Titanium Aluminide is 40% lighter than inconel. that's one point for Ti-Al and the marketing dept.

wow, Ti-Al isn't as strong as inconel at higher temperatures so the wheel looks different than the Garrett wheel.



different in more than 3 ways but we will focus on 3.

if you look at the wheels closely you will see that the BW wheel is a "fullback." it has a supportive bottom connecting the vanes. beefy, heavy, probably necessary to support the material. check out the Garrett. one point for Garrett

not as noticeable without your vernier caliper... the hub mass is much thicker on the BW. hubs don't convert much exhaust flow to power. they effectively shorten the working part of the wheel. another point for Garrett

finally, because Ti-Al isn't as stout as inconel the vanes need to be thicker and more limited as to shape. i asked Precision Turbo's chief engineer, Dan Barlog, if they had tested Ti-Al for turbines. he said "yes, but we chose flow over weight." they could not form the wheels into the shape they wanted and have them stay in one piece.

i add again that weight isn't even as much of an advantage since more material is needed.

Borg Warner told me... do not run over 1765 F. this was a face to face conversation. when i asked why the new number, my BW engineer said, it wasn't new, it was in the 220 page white paper... i didn't think so then and i haven't yet been able to find it... (this was in 2023.) we are directed by BW to not top 1765. that presents problems for the rotary. three points for Garrett.

i admit i haven't heard of a BW wheel failures but wheels get pretty plastic at high heat.

that all said, i really like the G40-900 for you. it is 600 rotary tops but is at the very edge (54) of the spool/trim range greatly favoring spool. my 1150 is at the other end but it is for the Texas Mile so spool isn't a factor. the only diff (62 mm V 71) in the two turbos is the inducer. the exducer is the same. BTW, i think mine spools like crazy.

you can get caught up in the numbers (like i do) but how does it do as to backpressure?

i made 674 around 8200 at 22.7 psi and my backpressure was 37% more than boost. at lower power levels it will be less. that's w a 3 inch exhaust and wastegate into the downpipe.

 

Howard thanks for your response. The g40 1150 maybe be more lagy than g40 900 but dont you think will be at least better in spool than my currently gt4088 journal? Also what is your opinion on g35 1050? Mayby better in spool but afterall will be smarter choice to choose g40 series that the engine will breathe better? Thanks

 

in 2013 i ran the Garrett hybrid GT4094r. it was wonderful. it was on my car when we ran 203 mph on the dyno. 8500 in fifth/T56. it was ball bearing. i don't have any experience w the 4088. most people don't see a need for 600 on a road course... but most people are most people. so it depends on what you want from your car. both G40 turbos are wonderful.

i think the G35 1050 is an amazing turbo. it can make more power than the G40 900 but i do think the hotside is just a bit too small for road racing and above 600. at 500 i think it could rip your head off as to spool. i do think it is the current ultimate turbo for the 400-500 consumer.

 

Would the new g35-900 not be the choice for ultimate response with power capacity?

I think it's a shame they don't have a G40 option around 66mm inducer. But the billet 62 flows plenty and those long blades lift air at lower shaft speeds.

 

HAHA now your talking. The GT4094R, What a wonderful turbo. I remember your project back then. Remember when we talk about my project in the old days? I was inspired by your project back then. My problem is that I have high egts now even with turbo blanket and heat shield. So i thought that replacing my turbo with a more efficient one will solve this problem and maybe my engine breathe better in that area around 550-600. also with a modern turbo better spool and better more breathable on high rpm at my 8500 limiter. So at this area you think g40 900 or g35 1050 will be safer and smarter choice. Here is a vid of my current setup after the session has ended. lot of the mods was from your knowledge and experience back then. A big thank to all of you. Looking forward for changes and even greater results.

 

The G40 will have lower drive pressure and exhaust manifold gas temperatures than the G35-1050.

What AFRs/injection mixes and timing are you running?

What temperatures?

 

just looking at the compressor maps, the GT4094R and G40-900 look pretty similar,
they both flow 80lbs/min maximum, they both are ~50lbs minute at 2 bar...


and the G40-900


the G40 turbine looks like it flows more at a lower PR, not sure what that would do, but it would be easier to hit that...
the PR is pre-turbo pressure vs post, so not many people measure that.

 

Not a lot in it with the 94, barely worth the swap, but his 88 compressor doesn't have the same flow capability.

 

Do you think replacing over gt4088 journal bearing not over the gt4094r will be massive upgade both in egts, spool and power.?

 

I don't think it will be drastic, however going to roller bearing and a lighter more efficient compressor and turbine should improve response and top end EGTs. If you were trying to push towards 600hp the difference in backpressure/temperature in the top end would be more noticeable than mid 400s.

 

Do you think choosing g40 1150 will be drastic change with 0.91 a/r for better spool and higher hp at faster times at lower boost pressures than my gt4088?

 

i wouldn't want to kneecap the G40-1150 w the .91. it puts out too much air at low pressure ratios.

 

Howard can you be more specific with a comparison of g40 1150 with. 91 ar vs the 1.06 ar and vs the g40 900 with 1.06 ar about possible rpm spool and 100 - 200 times at 1.4 bar and 1.6 bar boost?
Thanks

 

"Howard can you be more specific with a comparison of g40 1150 with. 91 ar vs the 1.06 ar and vs the g40 900 with 1.06 ar about possible rpm spool and 100 - 200 times at 1.4 bar and 1.6 bar boost?
Thanks"

sorry Mike, i have no specifics.

 

You may find some insight on the raceonly Facebook page, I think they have posted dyno graphs of g40-900 and 1150 and tirbo around that size on similar engine packages.

 

A G40-900 with the 0.85 or 0.95 A/R T4 twin scroll turbine will be the cat’s meow. It will blow the G35 out of the water. I’d recommend the original Garrett over the Pulsar copycat, the cost difference matters.
.

 

g40 900 with .85 or .95 a/r isnt too small at high rpm?

 

You have to remember the turbines flow like an old gt42

 

what do you mean they flow like old gt42? Are newer models more efficient?
A g40 900 with .95 ar or .85 ar wont have breathe issues at high rpm and create backpressure of exhaust?

 

There are no black and white answers. The tighter the turbine housing, the higher the pressure required to drive flow towards choke or overspeed limit on the compressor map. Everything is a compromise. For the 900 compressor on an extend port I think that’s a pretty good compromise.

If you download a Garrett catalogue you can compare the G series turbine maps to the GT series maps. The same diameter G series turbines have significantly higher flow due to revised design.

 

have you ever tried or have any info about the pulsar turbos? i am talking about g40 900 and g40 1150 options. Are those two have issues at high rpm and the possibility to fail at high egts and the possibility to destroy the engine since a blade will run into the engine?

 

Mine is still on the shelf but there is a lot of Australians running PSR turbos, including G40 on Japanese, euro and Australian turbo cars.