RB20 turbo upgrade

[Cornloaf]

Sorry to ask such a stupid question, but i am not so familiar with turbo sizes and flanges and a/r ratio, etc. I was just wondering what a good bolt on upgrade would be for rb20. I have heard rb25 turbo and z32 turbo are good bolt on upgrades, but how much hp gain should i expect from these. would a gt30R bolt on, and if not how about Garrett GT2871R. I am looking to get somewhere near 400BHP. Thanks for any info and your patience.

[Slo_240sx]

A gt30r turbo will be too big to fit on the stock manifold. You will need a custom manifold and wastegate if you want to go that big. Also If you buy the turbo you can get it in whatever exhaust flange you want to match your manifold. Ex 4 bolt in 5 bolt out, very popular because you can stay with a internal wastegate. 4 bolt 4 bolt out, needs custom downpipe. And a 4 bolt T4 flange, with a V-band.

I think you need something like a disco-potato turbo which is the GT28RS. They spool very fast sounding like something in your neighborhood and they aren't as expensive as the bigger GT turbos. Just make sure you don't get a T3/t4 and such because those are dinosaur prehistoric turbos.

-Alex

[y3llows14]

GT28R has T25 exhaust size. So no. That would defeat the purpose of smaller exhaust side for quicker spool up. Why wouldnt a GT30R fit, not much difference in size when comparing to any T3/T04E. You might need an adapter box for wastegate though.

[Wulfgang]

GT28R has T25 exhaust size. So no. That would defeat the purpose of smaller exhaust side for quicker spool up.

Can you explain yourself here? What's the problem with the T25 exhaust?

Also, don't forget about the S15 turbo, which outperforms the disco potato when installed on SR20s and keeps the OEM water cooling jacket.

[y3llows14]

Whats there to explain? Rb20 and Rb25 has T3 housing/flanges, why go through the trouble? When Slo240 said that you can put a T3 housing on the GT28R, that would defeat the purpose of having the turbo in the first place---good spool up!

[mmatl16]

I have heard rb25 turbo and z32 turbo are good bolt on upgrades

why do people keep saying this? it doesnt work guys. am I the only one who's tried this?

[y3llows14]

I think he meant Z31?

[goofynick6]

t3/t4's are not dinosaurs, they're just good technology that is still keeping up with competitors today. Yes, GT's are nicer, but they're a bit more expensive.

A t3/t4 t04e with .48 a/r turbine and .60 compressor with 50 trim compressor wheel would be perfect for the rb20 based on my current turbo and how it performs.

Nick

[Wulfgang]

I need clarification on a few things:

1. Is it true that turbos that fit SRs (S15, GT28R/RS) will not fit the RB20 mani because RB is T3 exhaust, but SR is T25 exhaust?

2. RB25 and Z31 turbos fit, but not Z32, correct?

And Nick, I know you've had success with your setup, but what would the equivalent turbo be in today's technology (maybe like a GT3071R?)?

[mmatl16]

[QUOTE=Wulfgang]2. RB25 and Z31 turbos fit, but not Z32, correct?QUOTE]

i think im bout to put this in my sig....

rb25 turbos do not bolt on to rb20's

1-would need a new downpipe2-different bolt pattern3-steering column is in the way4-do you want me to keep going?

[Wulfgang]

More clarification needed. I could care less about the turbine output bolt pattern.... the stock dump pipe bumps the steering on the RB20 anyway, so what do I care if the RB25 turbo needs a different dump pipe too?

What I really want to know is what turbos bolt up to the exhaust manifold. RB25? Z31? Z32?

The rest of the stuff like dump pipe, oil lines, water lines, etc. are going to probably be custom anyway, but keeping the RB20 exhaust manifold is important from a cost/reliability standpoint.

[mmatl16]

ok well rb25 does not...i repeat does not bolt up to the stock exhaust manifold.

and what are u going to do about the steering column if it did?

[WDRacing]

I agree with Nicks choice accept I would go with the .63 AR Ex housing. It is more efficient and gives more room to grow. The lag will be slightly more, but nothing bad.

[goofynick6]

Yeah, I have the .63 exhaust, stage 3 wheel on mine, but it just spools a tad slow for fun on the street. Granted mine is a 57 trim, but it's similar. With the fmic kit and piping, I get 15psi by about 4300rpms, kinda late, but it screams after that.

The GT30R would be an awesome turbo on the rb20, and would be nicer than my 57 trim by a lot I'd guess.

Here's a program I made to plot out points on compressor maps. It works great and has a lot of different common turbos in it. Directions are at the bottom of the first page(tab); type in the points there and then goto the other tabs to see how the points plot out.

http://filebox.vt.edu/users/ni...1.xls

Nick

[WDRacing]

I wonder how much of a difference the 50 trim would instead of the 57. I get full boost by 3200 on my KA and thats with 2 degree's of retard per lb. Only cause she hasn't been tuned yet. My clutch is spent.

I had a full frame TO4E with a .81 AR Ex on my GTS-t and it hit boost by 5300 or so.

Perhaps its the RB20 Mani. Not a very good design, fairly restrictive.

[Cornloaf]

so when you guys say bolt on, are you saying it just bolts to manifold and not 02 sensor housing?? Am i going to have to get custom 02 sensor housing either way? Also will the gt30R bolt straight to manifold with no adapters?? If i have to change 02 sensor housing anyway, i might as well just save up for gt30R. Also what is a good turbo that is completely bolt on, without having to change 02 sensor housing that i will see most hp from?? Thanks

[y3llows14]

i think im bout to put this in my sig....

rb25 turbos do not bolt on to rb20's

1-would need a new downpipe2-different bolt pattern3-steering column is in the way4-do you want me to keep going?

Well to be honest with you, those are just minor things that will occur in a Rb25det as well. Both are T3 flange, so it should bolt up. The problems are the location of oil and coolant lines. The dumpipe will have to be modify in either engine to clear the steering column. So they do bolt up, just need a little "tweaking". So Z31 and RB25det turbos should fit. For upgraded turbo, Im using precision GT3251E. Turbo is very responsive and hits full boost by 3800 rpm in 2nd gear (in my Rb25).

Edit...sorry for the confusion...I was only quoting the person that was saying it. I was sayint that RB25det turbo does bolt up!
Modified by y3llows14 at 9:52 AM 4/8/2005

[Sil240]

Hey the RB25DET does bolt up i have done it alreadyI can't tell you if the elbow clears the steering column or if the down pipe is in the same place, but i definetly bolted the RB25DET turbo to my RB20DETI have pics if you would like to seeI just can't host them so if someone wants to host it for me I can e-mail it to you

i think im bout to put this in my sig....

rb25 turbos do not bolt on to rb20's

1-would need a new downpipe2-different bolt pattern3-steering column is in the way4-do you want me to keep going?

Well to be honest with you, those are just minor things that will occur in a Rb25det as well. Both are T3 flange, so it should bolt up. The problems are the location of oil and coolant lines. The dumpipe will have to be modify in either engine to clear the steering column. So they do bolt up, just need a little "tweaking". So Z31 and RB25det turbos should fit. For upgraded turbo, Im using precision GT3251E. Turbo is very responsive and hits full boost by 3800 rpm in 2nd gear (in my Rb25).[/QUOTE]

[lmnhed]

Think of garret turbos with different sized rectangle flanges depending on the application. They have t2 flanges, t3 flanges and t4 flanges. The flange I am talking about is the one where the turbo bolts to the manifold.

T2 flanges are found on SR turbos, CA turbos, Z32 turbos, and RB26 turbos(i think, haven't had any personal experience with these) T2 is the smallest "rectangle" of the bunch

T3 flanges are the ones found on RB20's, RB25's, 84'-86' Z31 turbos (not sure about the later Z31 turbos), a t3 flanged turbo is also found on countless other cars, saabs, volvos and so on.

T4's are just huge so don't worry about it right now.

Anyways, I am sure that was overkill, but you can pretty much bolt any T3 flanged turbo onto a T3 flanged manifold. In your case you'll need to make sure the turbo you are getting has an internal wastegate, since that is how the facotry turbo is set up. Any non RB turbo is gonna be about the same amount of custom work as any other, IE custom lines, custom O2 pipe, etc. I have an 84' Z31 turbo on my RB20 right now, if you have any questions just ask, but after all the work I went through making the Z31 T3 work I wish I would have done a T3/T4 hybrid like these guys are talking about.

[mmatl16]

[QUOTE=Sil240]Hey the RB25DET does bolt up i have done it alreadyI can't tell you if the elbow clears the steering column or if the down pipe is in the same place, but i definetly bolted the RB25DET turbo to my RB20DETI have pics if you would like to seeI just can't host them so if someone wants to host it for me I can e-mail it to youQUOTE]

I dont know if u put the turbo on before u put the motor in but im telling you guys I tried to do it not even 2 months ago and it doesnt work.

I would be interested in seeing those pics though.

[Slo_240sx]

I haven't messed with an rb20 yet but since they're both t3 flanges I wouldn't see why they wouldn't "BOLT" up. Getting everything else on is a different story though

Oh just found this zerothread?id=111030 People say it fits with no prob... maybe you had your turbo upside down? LoL J/k...

[AR31TU]

Hey the RB25DET does bolt up i have done it alreadyI can't tell you if the elbow clears the steering column or if the down pipe is in the same place, but i definetly bolted the RB25DET turbo to my RB20DETI have pics if you would like to seeI just can't host them so if someone wants to host it for me I can e-mail it to you

[/QUOTE]

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