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Discussion Starter #1
So a little back-story first I guess....
I recently built a D16a6, with the intent to turbo it. The project was purely for fun, with no intended purpose. I was looking for somewhere around 300whp. I bought a Garrett GT28RS. The engine ended up blowing up on me at the track before I ever got around to using the turbo.

For a replacement engine, I decided to go with the D15b vtec. My plan is to keep it completely stock internally (other than ARP headstuds), and just low-boost it. Since I now have an intended purpose (having fun at the track), I'm not looking for ridiculous power. I just want around 200whp and as much torque as I can manage to squeeze out (180-200wtq would be sweet!)

I had initially thought that the GT28RS would be too big for my new goals, and figured that I'd be better off selling it and getting a GT25 of some sort. I wanted to stick with the Garrett GT line since I already have all the coolant line parts and I know that I can get the housings to work with the manifold and downpipe that I had made for the GT28RS.

To help me make an informed decision, I searched through the FAQs here and learned how to read compressor maps (finally! lol). I'm not sure if it helped or hurt though, as I'm now stuck not knowing where to go with my new-found knowledge. So I ask you guys to look over my calculations and lend some advice. Thanks in advance! Here we go.....

So my 3 options right now are:
1) GT2554R (GT25R)
2) GT2560R (GT28R)
3) Keep my GT2860R (GT28RS)

From what I've read, 9 PSI seems to be a safe number to use for a stock D-series. So I used that number, and the information found here: Compressor Map Reading For Dummies and I generated this comparison:



Just so you know where the lines came from...
at 3600 RPM (50%) I'm at 10lb/min.
at 5400 RPM (75%) I'm at 15lb.min.
at 7200 RPM (100%) I'm at 20lb/min.

The blue lines show where they would be making full boost. Per this table the turbos make full boost at:
GT25R = ~2600 rpm
GT28R = ~2800 rpm
GT28RS = ~3000rpm

I'm still very much a noob when it comes to this stuff, but to me it looks like I should just keep the GT28RS. My initial worry was that it was going to be too laggy at he low end, but according to these calculations, it's only a few hundred rpm's behind the smaller turbos.

Anyway...if you read through all of that...thanks!
If you read through it all and have some insight for me...thanks even more!
 

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Discussion Starter #5
Thanks for the info. And thanks for providing the dyno graph for reference. It's good to know that you're running the same engine as I am.
If I may ask....what else do you have done to your engine? If it's stock internally, how long have you been running it? Any issues?

As for the exhaust housing....is there a way that I can verify what I have? When I bought the turbo from Spoolin'Performance a couple years ago, they incorrectly labeled the turbo on the receipt, so I don't have any accurate records. I did measure the wheels though, if that helps.

Compressor: Exd wheel-60.13mm, Ind wheel-47.20mm
Turbine wheel: 53mm

Besides leaving room for more power in the future...are there any other reasons to use the GT28RS over the others?
 

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It should be stamped right on the the turbo housings on each side. If it isnt then the exhaust housing will be alot smaller.

Ive been running it for a few months now. Only issue I had is that I didnt have a small enough oil on it so it started to blow some smoke so make sure you get the .035 hole in it.

I got a skunke throttle body and intake manifold both at 68mm with 440's and a 2 1/2 inch cat back. I also checked the block and everything still looks good in there.

The only other thing I can think of between the two turbo's is that the rs has a much broader range the few hundred rpm's shouldnt make much of a diff as you should still be in the boost range between shifts at high rpm's but i would find a dyno on the rs and see when it spools and make your decision from there. Also if you do head work the 2554 might become inefficiant at high rpm's. The 2854 is supposed to be better then the 2554 in higher rpm's but thats just what i read.
 

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Oh another thing is that the intake housing on the GT2854 was not ajustable so the oil port doesnt sit straight down. You have to take the housing off and then figure out a way to pull off the snap ring so you can set it properly. Im not sure if the GT2554 is the same. But im guessing it is as they use the same housings just the 28 has more or less fins on one of the fans i cant remeber.
 

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I would avoid the GT2554R as the others will spool just as well and make more hp. Matter of fact the GT2554R and GT2560R use the same turbine just a different compressor.

I have run a GT2560R on a Toyota 4AGE and it was OK in my opinion. I thought it should have spooled better but I then again I was on my own when it came to tuning and I know some minor faults I made. Still it could have done a lil better. Having said that the GT2860RS will spool a lil slower then GT2560R but honestly if you already have it I would try it out. They are both very good turbos and if properly executed should make you more then happy.

Somethings to consider with your modest goals are keeping the IC'r plumbing as short as possible and I would keep the tubing around 2" and no more then 2.25". Most assume bigger is better but that is far from true. Using a smaller sized tubing will help pick up response.
 

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Discussion Starter #9 (Edited)
d~nice: Ok cool, I'll check the housing for any markings.
I do already have the .035 restrictor, so I should be good there. I also have 440's like you. My Performer X manifold is ported to 62mm to match my ITR throttle body.

But yeah, any shifts done at high rpm's should definitely keep me within the boost range with any of these turbo's. The 3-400 rpm difference at the low end shouldn't make too much of a difference I would think.

As for being adjustable...you're talking about the middle portion right? If so, the GT28RS is definitely adjustable, so I should be good there too.

As for checking dyno graphs to see when a turbo spools....is that different than my blue lines on the compressor maps up above?
 

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Discussion Starter #10 (Edited)
mhamrick: Thanks for your input man. Yeah, since I already have the GT28RS, I'd really like to be able to use that one instead of dealing with the hassles of selling it and buying a different one.

For the intercooler, I do have a backdoor type setup, so that will definitely help keep the piping lengths to a minimum. The intercooler is setup for 2.5". I had intended to go with 2.5" for the charge piping. You're thinking this is a bad idea?

While we're on the subject...I get conflicting advice on exhaust piping diameter too. Some say 2.5" is enough. Some say to go with 3". Blah....
 

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exhaust piping 2.5 should be fine up to 300 hp and if you want to go beyond that you will need it to be bigger.

Ya with the dyno and your markings it be prety much the same. I just like to real world app. Also the rs is alot more efficient then the others so it will make better power.

Ya the intake side of the 2854 did not have bolts to adjust it so you needed to pull off the exhaust housing then move the snap ring so you can adjust the intake housing so the oil drain would point down. Even after this the intake side pointed straight towards the intercooler with the wastegate on it which made it tough to hook up the intake piping without making all sorts of angles and bends.

Im using 2.5 piping as well so you should be fine there. But its good to know that 2 inch pipen will help spool up time.
 

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Some people actually see gains on sub 300whp setups with larger ic'r plumbing. Its not the diameter as much as the larger radius smooth flow out. Realize that the intercooler and plumbing is volume that the compressor has to fill. This is the reason why Subaru uses top mount and the shortest possible plumbing.
 
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