HKS GT3040 VS Garrett GT35R/GTX35R

[rayaapp2]

So Im looking at a GT3040 HKS turbo with T3 flange for my RB25.

My biggest issue is that I cannot locate a compressor map to just do the math.

So first off, anyone have a compressor map for one of these turbos?

Second if anyone knows how do these GT3040 turbos compare with the GT35R. My personal preference is the GTX35R for my goals, but I already have a GT35R. From what I understand the compressor on the GT3040 is comparable to the GT35R but the turbine is closer to a GT30.

 

Can anyone shed some light on the differences or possibly post up a compressor map for the HKS unit?

 

Thanks

 

Ray

 

 

Edited November 11, 2012 by rayaapp2

[ZT-R]

Good luck finding hks maps. I would think that would choke.

[240zdan]

Hmm having tried both the precision 6235r and the precision 5830r on my rb26, I would say the gt3040 would be a bad combo, the turbine would just choke it at higher revs, and the larger compressor wheel would just introduce unnecessary lag. Hybrid turbos are silly if you ask me, I would say use your gt35r and stop trying to research like a mad man, way too many people spend way too much time researching junk like this instead of bolting on a turbo and driving it hard, the differences will be minor and you will be happy with the 35r and can always sell it and get a 30r if you find the 35r is too laggy.

[rayaapp2]

It appears its basically a Garrett GT3076R same specs as far as I can tell. Dual Ball bearing.

I also have a GT3076(I believe as its untagged other than its stamped garrett) which is almost identical except it a thrust bearing style and the compressor side housing is slightly different in that the inlet is smaller but the compressor is identical.

[ZT-R]

From what i read the 3076 is kind of a missmatched turbo. I would personally stick with the gt35 if i were you.

[240zdan]

How is the 3076 a mismatched turbo?

GT3076r (GT30r) = GT30r turbine with 76mm compressor wheel exducer

GT3582R (gt35R) = GT35r turbine wheel with 82mm compressor wheel exducer

 

Not mismatched, just smaller over all. It all depends what he wants, if he wants more usable torquer and a fun street engine, go with a GT3076, if you want more peak power and drag race a lot, go with the gt35r. I personally have tried both in billet configurations and prefer the gt3076r, its great on the rb.

 

The GT2876R would be a "mismatched" turbo, or a t3/t4 60 trim with a .48 ar turbine housing for example.

Edited November 19, 2012 by 240zdan

[rayaapp2]

I have a GT35R knockoff single ball bearing turbo. Its brand new. Its definately no Garrett though.

I have seen these knock off turbos before on RB25's, but I dont think they really compare to the genuine article. Im guessing its all in the tollerences, though I have to say they do well for something thats less than 1/10 the price.

Based on compressor maps I really wanted to get the GTX3582R over the regular GT3582R.

In the end for what I want to do with the car(which is a little track and a little street) I will be shooting for that GTXR3582R with one of the smaller A/R's(because Im using stock cams that drop off around 6800-6900rpm). For now I have these three other turbos. Out of the three Im guessing the GT3076R is probably going to be the best choice for me. Its ball bearing, and high quality so in theory it will take the abuse I give it and it should have a good spool time on the RB25. All three have a .63 turbine though.

 

Now I have to figure out which manifold to run, because the best fitting manifold is also the cheapo China made one not the LoveFab I bought which I would prefer as its higher quality material.

[rayaapp2]

So I ended up with the GT3076R and the CXRacing manifold on the car currently.

I figure as 240Zdan stated it will be fun to drive around as a street car. Id like to give it a shot and see how I like it for now.

 

Im still planning to use the Love Fab after some corrective measures are made and Id like to install a GTX3582R

 

Ive just realized though that I dont know how to calculate anything for the turbine side for choosing proper A/R for the turbine. I dont imagine its the same set of calculations used for the compressor. That doesnt make much sense. So thus far Ive been using educated guess's based on the few cars I have driven with RB25's and GT35R's. The GTX is different than a regular GT35 but Im guessing I want a smaller A/R so Im tossed up between the .63 and the .82 A/R's. Im not sure I know where to start on figuring this out. My goal is to get quick spool response that stays efficient to 6900-7000rpm's where the stock cams tend to poop out.

 

Ill test out the two turbos and figure out which one will stay on the 260ZR project and which will find its way to the 910R NEO project that's been simmering on the back burner.

 

Im also guessing the CXRacing manifold and the love fab manifold will both play heavy rolls in the performance of the turbo. I dont predict that the GTX3582R will do well in any trim other than the .63 on that manifold. Its downfall is that it has small tubes and poorly fit joints that restrict flow where the lovefab will excel with its uber large tubes and artistic joints. Its really messy inside the CXRacing manifold and there isnt much that can be done to correct it.

 

Id like to figure out which turbine A/R to run with the GTX3582R though so I can reduce lag as much as possible as far as the turbo is concerned.

[240zdan]

Id personnaly run a .82 ar on both the 30 and 35.

I have expermineted with a .63 and found that the reduction in lag is not worth the sacrifice in topend and midrange power.

the .63  is better suited for a small 4 cylinder such as a honda b18 or similar.

A properely designed manifold, free flowing exhaust, free flowing intake and porper tune will be more important than stressing over the ar.

The .82 will just make more power overall.

The gt3076 will be a fun turbo on your stock rb25. If youre interested, I may  have some turbine housing I could offer up for cheap for both 30 and 35 wheels in both ars

[rayaapp2]

I would be interested in seeing a T3 turbine for the GT3076R with the .82. 4bolt or clamp style flange? I have a 4 bolt flange with a .63 turbine now I believe.

 

PM with some details Id be interested in at least exploring the options.

 

The 260ZR has a slightly modded engine. Nothing extreme. I will likely stick the GT3076R on the NEO engine thats being prepared for my 82 910.

[Gollum]

 Hybrid turbos are silly if you ask me,

It really depends on the application. In a "perfect" world you're choosing your hot side based off the engine it's going into, and how it would perform in NA condition, and the cold side based off of how much power you'd like to make. For example, a .63 T3 isn't going to choke a stock L28, but the typical T3 compressors aren't going to make as much power as people around these parts are looking for. Even the largest T3 sized compressors aren't going to support 400+hp, which you're knocking on the door of if you're pushing 325+ to the wheels.

 

And really, I think you're over-generalizing that a small turbine AR is going to choke mid range and top end power. Look at rally or vintage F1 turbo setups. They run/ran turbine sizes small enough to get more than enough boost off idle, and then size the compressor to reach the top end they're looking for. The only reasons to feel a small turbine AR is going to "fall off" is that either 1. You don't have a large enough wastegate, or it's not properly designed), or you're mistaking earlier power for less power. Many times the fact that a larger turbo hits harder and later, is mistaken as "more" when that isn't necessarily the case.

 

I've see a stock, unmodified VF39 (sti oem) turbo put over 350 to the wheels in a STI, which is almost 100 more than many people expect as "the limit" for the stock turbo. Was this turbo "choking" at the top? Hell yes! But that was an issue at the compressor side, not the turbine. We didn't have a pressure sensor on the manifold, but I'd be willing to put money on the fact that it wasn't absurd. I'm sure we'd have made even MORE power from it if we'd installed an external wastegate and pulled a few other tricks we hadn't touched yet, but we moved on to a larger turbo after a sweet deal on a longblock came up. Oh, and to really piss people off we were running the stock intercooler.

 

Speaking (or typing, more literally...) about this reminds me of Big Phil's whole saga about which turbo to run. He was having surge issues with a turbo and found that going to a turbo with a larger turbine AR made it go away. The main issue was that he was developing too much boost too early for that compressor. Sure, he made "more power" with the larger turbine AR, but that's simply a function of the fact he was able to run more boost since he wasn't surging the compressor wheel because boost was hitting later.

 

Even garrett themselves in their literature state that the biggest issue with too-small of an AR on the turbine's main issue is excessive back pressure causing the engine to choke.... This IS NOT an issue with a correctly designed wastegate. AND, even still, I've seen plenty of engines that continue to make power with pressures at the exhaust upwards of 2.5 BAR while they're not even running 1.5 BAR on the intake.... Like I said, it's really about perceptions of power and where it comes in. Of course an engine is going to feel like it's "choking" if you've added extra power up front when there isn't power to be gained up top, giving yourself a flat HP curve. 

 

Well, that's my 2 cents. All that said, ray, you've got plenty of turbos to play around with before you bite the bullet on any purchases. And remember, there's many ways to skin a cat when it comes to spool time, so don't fret if the turbo sizing you like doesn't seem responsive enough, 

[rayaapp2]

There are so many dynamics to a turbo charger. I guess that is half the fun.

As far as choking goes, the stock turbo on the RB25 is something like a hybrid GT28 and the turbine A/R is close to .46 or .48(unconfirmed) with a smallish turbine wheel. I didnt measure the exhaust back pressure pre turbo, but I was getting readings of 2100+ deg F in the manifold on the pyro gauge under hard pulls. All the RB25's Ive driven with larger turbos have had some serious lag. Even the ones with good components and great tunes.

One of my goals with this build is to get the power and keep it as streetable as possible so its a total no-brainer to drive even if my wife climbs into the driver seat.

 

Ray

[240zdan]

It really depends on the application. In a "perfect" world you're choosing your hot side based off the engine it's going into, and how it would perform in NA condition, and the cold side based off of how much power you'd like to make. For example, a .63 T3 isn't going to choke a stock L28, but the typical T3 compressors aren't going to make as much power as people around these parts are looking for. Even the largest T3 sized compressors aren't going to support 400+hp, which you're knocking on the door of if you're pushing 325+ to the wheels.

 

And really, I think you're over-generalizing that a small turbine AR is going to choke mid range and top end power. Look at rally or vintage F1 turbo setups. They run/ran turbine sizes small enough to get more than enough boost off idle, and then size the compressor to reach the top end they're looking for. The only reasons to feel a small turbine AR is going to "fall off" is that either 1. You don't have a large enough wastegate, or it's not properly designed), or you're mistaking earlier power for less power. Many times the fact that a larger turbo hits harder and later, is mistaken as "more" when that isn't necessarily the case.

 

I've see a stock, unmodified VF39 (sti oem) turbo put over 350 to the wheels in a STI, which is almost 100 more than many people expect as "the limit" for the stock turbo. Was this turbo "choking" at the top? Hell yes! But that was an issue at the compressor side, not the turbine. We didn't have a pressure sensor on the manifold, but I'd be willing to put money on the fact that it wasn't absurd. I'm sure we'd have made even MORE power from it if we'd installed an external wastegate and pulled a few other tricks we hadn't touched yet, but we moved on to a larger turbo after a sweet deal on a longblock came up. Oh, and to really piss people off we were running the stock intercooler.

 

Speaking (or typing, more literally...) about this reminds me of Big Phil's whole saga about which turbo to run. He was having surge issues with a turbo and found that going to a turbo with a larger turbine AR made it go away. The main issue was that he was developing too much boost too early for that compressor. Sure, he made "more power" with the larger turbine AR, but that's simply a function of the fact he was able to run more boost since he wasn't surging the compressor wheel because boost was hitting later.

 

Even garrett themselves in their literature state that the biggest issue with too-small of an AR on the turbine's main issue is excessive back pressure causing the engine to choke.... This IS NOT an issue with a correctly designed wastegate. AND, even still, I've seen plenty of engines that continue to make power with pressures at the exhaust upwards of 2.5 BAR while they're not even running 1.5 BAR on the intake.... Like I said, it's really about perceptions of power and where it comes in. Of course an engine is going to feel like it's "choking" if you've added extra power up front when there isn't power to be gained up top, giving yourself a flat HP curve. 

 

Well, that's my 2 cents. All that said, ray, you've got plenty of turbos to play around with before you bite the bullet on any purchases. And remember, there's many ways to skin a cat when it comes to spool time, so don't fret if the turbo sizing you like doesn't seem responsive enough, 

 

 

Im  not over generalizing anything.

I stated hybrid turbos are silly. I was mainly referring to a turbo with a small turbine wheel and large compressor wheel. Why run a huge compressor wheel that is capable of flowing more than the turbine wheel, putting it into surge territory, increasing IATS, increasing exhaust manifold pressure, decreasing power. I was just stating that compressor wheels and turbine wheels shoudl be proportioned to eachother, and this is the route many people are going with...

The turbine housing thing, you have your reasons as to why a smaller turbine housing my be better and thats fine, but I am speaking from experience. The larger turbine housing  doesnt spool much slower and makes more power overall.

If a properely degined wastegate is the magic key then why do companies even offer different turbine housings as options.Besides, the wastegate is a simple valve, its the design of the manifold that matters more. Just like I stated in my post.

 

Youre so set on the fact that turbine housing AR doesnt matter, you are right, run the smaller turbine housing you can get away with and enjoy. Dyno sheets are the only things that will prove you wrong.

 

These are simple facts based off experiences. Whether or not the guy chooses a .63 or a .82 is none of my concern I am just speaking from my own observation.

Alot of the time I think people spend too much time thinking/arguing about this kind of stuff rather than laying rubber down.

 

Anywasy rayapp Im pretty sure I have a .82 for a 30r somewhere... just try out the .63 and see how you like it first, most likely youll barely even notice a difference between the too if youre not running crazy boost.

Edited December 29, 2012 by 240zdan

[rayaapp2]

These are simple facts based off experiences. Whether or not the guy chooses a .63 or a .82 is none of my concern I am just speaking from my own observation.

Alot of the time I think people spend too much time thinking/arguing about this kind of stuff rather than laying rubber down.

 

Anywasy rayapp Im pretty sure I have a .82 for a 30r somewhere... just try out the .63 and see how you like it first, most likely youll barely even notice a difference between the too if youre not running crazy boost.

 

is 22psi crazy? LOL

Seriously Im looking to push 18-22psi on the GTX35R to hit the flow numbers for the power I want in the 260ZR project. Im guessing I would be looking at a lower boost pressure on the GT3076R somewhere around 18-20psi. Im gonna be logging some serious dyno time playing around in my near future I think. Im not putting 325mm rubbers on the rears for looks under my new 280yz fenders.

 

From my limited experience you are both right if that makes a difference. There are aspects of both your arguments that I would disagree on, but Im not really looking for the argument.

 

I would be very interested in the .82 A/R turbine housing for the GT3076R I have. Id like to see the difference on the dyno between the two is to put this to bed for me. And If I decide in the end to go with the GTX35R some day I will have a choice of housing A/R for the lower boost (honestly probably 12-15psi ) on the 910R build and my homework will be done.

[240zdan]

http://honda-tech.com/showthread.php?t=2801402

heres a good idea of what the difference is like. now this is on a 1.8l mind you, the difference on a 2.5l would be amplified. as you can see the larger turbine housing offers about 10 more ft lbs but only about 200 rpms more lag.

 

Also Gollum: when you refer to f1 and rally turbos, how many of these turbo have you actually taken apart and inspected? I have a IHI RX8 cart turbo at work and I can tell you that the turbine housing is NOT small. Just wondering where you even get your information from.

 

Im not saying that bigger ar turbine housings are better im just saying the .82 is more suitable for the rbs, especially the 2.5l and 2.6l variants. if i was running a rb20 is run a .63. if i was running a stroked and cammed rb id run a 1.06 or possibly larger.

 

 I wish I could get a dyn sheet of my rb26 with the 30r and 35r in both .63 and .82 turbine housings but i can barely keep the thing on the road as it is... always something to fix

Edited December 29, 2012 by 240zdan

[Gollum]

Im  not over generalizing anything.

I stated hybrid turbos are silly. I was mainly referring to a turbo with a small turbine wheel and large compressor wheel. Why run a huge compressor wheel that is capable of flowing more than the turbine wheel, putting it into surge territory, increasing IATS, increasing exhaust manifold pressure, decreasing power. I was just stating that compressor wheels and turbine wheels shoudl be proportioned to eachother, and this is the route many people are going with...

Because there are other ways to prevent surge, some of which have been experimented with in motorsports since the 80's. Surge is caused by TWO axis of the compressor map, one of which is easy to control.

The turbine housing thing, you have your reasons as to why a smaller turbine housing my be better and thats fine, but I am speaking from experience. The larger turbine housing  doesnt spool much slower and makes more power overall.

I agree that the overall frame size needs to be well matched to your application, and the difference between .63 AR and .82 aren't enough to lose sleep over and you're better off just getting something in your car and going. And for the record I'd never run a grossly offset turbo, trying to spin a T6+ sized compressor with a T3 turbine. That'd be dumb. IF you can use that much air, you can push enough air to warrant the larger turbine that will have adequate inertia leverage on the compressor.

If a properely degined wastegate is the magic key then why do companies even offer different turbine housings as options.Besides, the wastegate is a simple valve, its the design of the manifold that matters more. Just like I stated in my post.

I never meant to imply that the proper wastegate was a magic bullet. As you state, the manifold design is EXTREMELY important, which anyone who's looked at turbo F1 designs should see. They put a LOT of work into their manifolds to ensure that gases would flow almost as well out of the wastegate as they did out of the turbine.

 

Youre so set on the fact that turbine housing AR doesnt matter, you are right, run the smaller turbine housing you can get away with and enjoy. Dyno sheets are the only things that will prove you wrong.

I never said they don't matter. Actually the opposite. I find that too many people use a larger turbine AR than necessary to avoid other complications. To me it's a band-aid and the largest reason turbos historically have such a bad reputation regarding lag. It's only with the more recent ball bearing and wheel improvements that we've seen people able to get away with cheaper/simpler setups, thus the stigma of "massive turbo lag" is slowly becoming a subjective thought to most people.

 

These are simple facts based off experiences. Whether or not the guy chooses a .63 or a .82 is none of my concern I am just speaking from my own observation.

Alot of the time I think people spend too much time thinking/arguing about this kind of stuff rather than laying rubber down.

Agreed. Also the reason when helping on a friends STI build we stuck with the stock turbo as long as possible, and might have broken a record making the power we did with the amount of stock parts. GET ER DONE!!! has been my philosophy as of late. But if we can make nearly 40% more power than others expect you can make on a turbo, I'd say that QUITE OFTEN people buy more turbo than they need, and tend to assume they need more turbine flow than they actually do.

 

Anywasy rayapp Im pretty sure I have a .82 for a 30r somewhere... just try out the .63 and see how you like it first, most likely youll barely even notice a difference between the too if youre not running crazy boost.

Agree. I don't think splitting hairs between the two will become an issue until you're asking for 400+whp from either. And even then, if you like the response of the .63 but find yourself hitting surge once over a certain RPM then you can look into solutions for the surge, or decide if the easy route of the .82 is the better option for you at that point.