Top RB20 Club... do you have over 260rwkw?

[TurkeySlapper]

yeah yeah i know its not an RB20 buuuut while we're on the subject of modded engines, can ppl who have experience with GCG hi-flows give me some feedback regarding power/response etc? I have a stock RB25 with FMIC and pod making 200rwkw and soon will have a PFC, a bolt on turbo upgrade is a very attractive option but i dont wanna fork out and get bugger all power increase. At least 230rwkw im thinking, will the 450hp turbo provide that?

P.S. i did have a 20 before i popped it, must say revs kick arse but id never go back to one.

[Sydneykid]

yeah yeah i know its not an RB20 buuuut while we're on the subject of modded engines, can ppl who have experience with GCG hi-flows give me some feedback regarding power/response etc? I have a stock RB25 with FMIC and pod making 200rwkw and soon will have a PFC, a bolt on turbo upgrade is a very attractive option but i dont wanna fork out and get bugger all power increase. At least 230rwkw im thinking, will the 450hp turbo provide that?

P.S. i did have a 20 before i popped it, must say revs kick arse but id never go back to one.

On an R34 GTT RB25DET Neo we have 265 rwkw out of the GCG ball bearing hi flow.

[Roy]

...

I don't want to sound like I am picking on plain bearing turbos, but yours displays the same symptoms I see often.  They build boost rapidly at highish rpm for their (small) size and then run out of airflow (because of this smallish size).  Looking at it the other way, if you had a larger plain bearing turbo, then the boost build would be even later but you wouldn't loose as much top end.   On the other hand the (larger) ball bearing turbo gives slightly better boost build, but it is still large enough to give a much better result at higher airflows (rpm).

Bottom line, it has been my experience that plain bearing turbos have a narrower power band, regardless of size.  Time for some cams, toughen up that top end.  

I have decided agaisnt cams, ill save my money for putting cams in an engine that actually makes power worthy of $1000 cams:)

As for plain bearing turbos, im not arguing, but the first thing to remember is that my turbo is running an exhaust housing that is equivelant to a 0.87-1.01 (approx in the Garret world) so i dont believe the response is a result of the bearing type.

More the use of a turbo sized for an RB25 on an RB20. Actually the turbo is a single off a GTR twin setup with larger exhaust wheels and exhaust housing. So in Jan when i get the recommended A/R housing for my RB20 it may be more indicative of how the turbo should perfrom.

Out of interest, direct comparison with your hi-flow:

165 7,750

175 7,500

180 7,250

195 7,000

205 6,500

209 6,000

222 5,500

216 5,250

198 5,000

174 4,750

132 4,500

I had to guess the values for the last few rpm points as the tuner called it quits, but to drive the car it definetely has plenty of legs up there, ill be sure that the next tune with smaller housing pulls all the way to the rev limit.

So the above numbers mean an average power of around 193rwkws for the same power band. So that is still ok average power. And that is with an overly rich tune, very conservative ignition and about 1.25bar.

At 3,500rpm i have about 3psi, at 4,150rpm i have about 8psi and 4,750rpm i have about 16psi. The smaller housing might have 16psi in by 4250rpm. Not sure, but at the moment the way boost comes in it means power is rather progressive with no traction issues, so even if im still 1-2psi short of full boost at 4,750rpm im still making 174rwkws.

I think the top end would be improved with more ignition and a better cat, maybe even removed for track days.

The more i consider my setup, the more impressed i am by the Trust TD06-20G. I think with the right A/R exhaust housing, ignition all sorted then i think the results will only improve.

Not saying this setup is ideal, but looking at the numbers and braking it down, it doesnt looking that bad, actually rather promising considering the changes ill be making the next few weeks:)

[Sydneykid]

I had to guess the values for the last few rpm points as the tuner called it quits

My experience with standard cams has been that RB20's feel OK over 7,000 rpm. They don't go flat like an RB25, but the power drops off a lot. You may be suprised when you actually measure it.

[Beer Baron]

The more i consider my setup, the more impressed i am by the Trust TD06-20G. I think with the right A/R exhaust housing, ignition all sorted then i think the results will only improve.

I have a bit of a soft spot for the ol' trust TD06 kits too. Having driven two SR20 powered cars, both with different versions of a Trust TD06 kit I'd have to say they are a pretty good thing. Value wise they are very attractive (cheaper to buy and cheaper to re-build).

Richard

[Roy]

My experience with standard cams has been that RB20's feel OK over 7,000 rpm.  They don't go flat like an RB25, but the power drops off a lot.  You may be suprised when you actually measure it.

Ok, i guessed a 30rwkw drop off over the last 1,000rpm. I thought i was being pretty conservative, i didnt think power would drop off near 30rwkws, but i suppose anything is possible. Would you happen to know a pressure instrument that i can use to measure the pressure in my exhaust housing. My current 10cm housing has a tapping, and i was going to do the same with the new 8cm housing im getting. I cant find an instrument with a analogue output that can handle up to 1000deg C that doesnt cost the earth??????

I was looking to measure the back pressure in the exhaust housing and log it with the data logger. I dont think the 8cm housign will be restrictive, but you never know, data speaks volumes more then seat of the pants.

My understanding is if im running 20psi, then i want to avoid exhaust manifold/housing pressure more then 50psi (approx 2.5 x boost pressure)???

[Sydneykid]

Ok, i guessed a 30rwkw drop off over the last 1,000rpm. I thought i was being pretty conservative, i didnt think power would drop off near 30rwkws, but i suppose anything is possible. Would you happen to know a pressure instrument that i can use to measure the pressure in my exhaust housing. My current 10cm housing has a tapping, and i was going to do the same with the new 8cm housing im getting. I cant find an instrument with a analogue output that can handle up to 1000deg C that doesnt cost the earth??????

I was looking to measure the back pressure in the exhaust housing and log it with the data logger. I dont think the 8cm housign will be restrictive, but you never know, data speaks volumes more then seat of the pants.

My understanding is if im running 20psi, then i want to avoid exhaust manifold/housing pressure more then 50psi (approx 2.5 x boost pressure)???

Hi, as you can see mine drops off 35 rwkw and the GTR cams lower this considerably compared to the standard cams. I have also spent a bit of time minimising the drop off with fuel and ignition mapping. This is a bit hard to do if you don't log it in the first place.

You can use a normal boost gauge to measure back pressure in the exhaust. Since it measures pressure (not airlfow) the hot air doesn't travel through the tube from the exhaust up to the gauge. You will of course need a heat resistant piece of hose at the exhaust itself and for a short distance thereafter.

As for back pressure versus boost, it really depends on the turbine pressure ratio and the exhaust. Following is an extract from an article written by Jay Kavanaugh, a turbosystems engineer at Garret. It made sense to me of what is a complex subject or aerodynamics that always makes my brain ache;

"Say you have a turbo operating at a turbine pressure ratio (aka expansion ratio) of 1.8:1. You have a small turboback exhaust that contributes, say, 10 psig backpressure at the turbine discharge at redline. The total backpressure seen by the engine (upstream of the turbine) in this case is:

(14.5 +10)*1.8 = 44.1 psia = 29.6 psig total backpressure

So here, the turbine contributed 19.6 psig of backpressure to the total.

Now you slap on a proper low-backpressure, big turboback exhaust. Same turbo, same boost, etc. You measure 3 psig backpressure at the turbine discharge. In this case the engine sees just 17 psig total backpressure! And the turbine's contribution to the total backpressure is reduced to 14 psig (note: this is 5.6 psig lower than its contribution in the "small turboback" case).

So in the end, the engine saw a reduction in backpressure of 12.6 psig when you swapped turbobacks in this example. This reduction in backpressure is where all the engine's VE gains come from.

This is why larger exhausts make such big gains on nearly all stock turbo cars-- the turbine compounds the downstream backpressure via its expansion ratio. This is also why bigger turbos make more power at a given boost level-- they improve engine VE by operating at lower turbine expansion ratios for a given boost level."

Hope that helps:cheers:

[dangerous_daveo]

And in laymans terms???

[Chris32]

And in laymans terms???

The bigger the dump/exhaust, the less backpressure and more power potential

[CerealKiller]

no love for the RB20 here (sorry again Roy).

Blitz front mount

A'PEXi pod

3" turbo back w/ hi flow cat

upgraded fuel pump

running 12psi got me a massive 138rwkw....RB25 here we come

[BlueRB240]

no love for the RB20 here (sorry again Roy).

Blitz front mount

A'PEXi pod

3" turbo back w/ hi flow cat

upgraded fuel pump

running 12psi got me a massive 138rwkw....RB25 here we come

Thats what I made with my RB20 but all I have is just exhaust and no cat. Stock intercooler. 186hp to the rear wheels at 10psi no boost controler.

[Roy]

Hi,  as you can see mine drops off 35 rwkw and the GTR cams lower this considerably compared to the standard cams.  I have also spent a bit of time minimising the drop off with fuel and ignition mapping.  This is a bit hard to do if you don't log it in the first place.

With the high flow does it hold a steady 1.25bar to redline? If so then yeh i probably have perhaps a 45rwkw drop pff:( Dunno?!?!) But my turbo doesnt have any probs holding that level of boost, so does feel as though the top end is still working:)

As for boost gauge, i may have to find an electonic one , as i want to read the voltages with the data logger, i dont know anyone thats willing to be a passenger who reads a gauge while i drive:(

...oh yeh and back pressure, have to do something about my cat:(

[ScottKing GTS-4]

Guys,

I've got an RB20DET with an R33 Turbo fitted, Hybrid FMIC, Turb back 3" HKS exhaust, TurboSmart Boost Controller, Cold Air Induction with a K&N Pod.

Next I want to chip it and dyno the thing to get the correct fuel maps, etc configured. I'm just wondering a) Where in your experience are some good places around Sydney to get an RB20DET Chipped & Dyno Tuned and B) Should I look at upgrading the fuel pump/injectors soon. I'm pretty sure the stockers will flow up to 200rwkw OK but I dont want to run into reliablility troubles with this engine.

Thanks in advance.

Havent Dyno'ed recently but I'm looking for 200rwkw

[Cubes]

200rwkw from a RB25 turbo on a RB20 with your mods is wishfull thinking.

Obviously depending on the dyno.

You could get very close but I think you would need a nice loud full free flowing exhaust, adjustable cam gears, a good tuner and around 1.1bar of boost at peak power.. None of this peaking at 1.1bar then dropping off in the higher rpm ranges (i.e what bleeders will do)

I also think you will need an adjustable fuel pressure reg as around 200rwkw the stock injectors tend to run a little lean.

I've guestimated 1.1bar of boost based on my experiences with how much better the rb25 head flows. For example my rb30det with the rb25 head makes the same power at 6psi boost as the rb20 did at 11psi. So thats approx 5psi difference.

An Rb25 will make very close to 200rwkw if not over with adjustable cam gears on 11psi.

11+5 = 16psi or ~1.1bar

But then the rb25's turbo efficiency at 1.1bar of boost may suffer so it may fall short..

Who knows, its really only a guesstimate. Be sure to keep us updated.

[Remix-]

What i don't understand is, why do so many people attempt to make high power using a fuel pressure regulator instead of larger sized injectors! These days grabbing a set of GTR injectors and a ballast resister isn't exactly a costly affair.

Running on 100% duty would make me feel nervous each time I drove the car.

Anyways, my current setup is:

HKS GT2535 turbo

Trust R-SPL fmic

ROM'd factory ECU

R34 GTR Injectors

Walbro 255lph fuel pump

90mm uninterrupted turbo back exhaust

Pod/Clutch/Lightened flywheel

Cold air induction/Heat shielding

Greddy Profec B spec 2

-

The car is currently being built up (second RB20DET). I expect that it should be ready in a couple weeks. I am aiming for 300+ rwhp.

[ScottKing GTS-4]

Yeah I was looking at fitting adjustable cam gears also as I heard there are pretty substantial gains that can be had on the exhaust timing particularly on the RB20DET. No doubt a set of cam gears will also help the Chipped ECU.

I made 155rwkw on the U.A.S. Dyno when all it had was a cat back 3" exhaust, boost controller and pod (stock turbo - 14psi, stock intercooler, stock front-pipe, no C.A.I.). So with these mods I hopefully should hit pretty close to 200rwkw - however I do not want to be running 100% duty on my injectors. I've heard of the stock injectors handling upto 220+ but not sure how reliable that is.

Not sure if I'd rather fit a fuel pressure regulator or just fit a bigger fuel pump. Probably fit a bigger pump, out with the old in the new right.

200rwkw from a RB25 turbo on a RB20 with your mods is wishfull thinking.

Obviously depending on the dyno.

You could get very close but I think you would need a nice loud full free flowing exhaust, adjustable cam gears, a good tuner and around 1.1bar of boost at peak power.. None of this peaking at 1.1bar then dropping off in the higher rpm ranges (i.e what bleeders will do)

I also think you will need an adjustable fuel pressure reg as around 200rwkw the stock injectors tend to run a little lean.

I've guestimated 1.1bar of boost based on my experiences with how much better the rb25 head flows. For example my rb30det with the rb25 head makes the same power at 6psi boost as the rb20 did at 11psi. So thats approx 5psi difference.

An Rb25 will make very close to 200rwkw if not over with adjustable cam gears on 11psi.

11+5 = 16psi or ~1.1bar

But then the rb25's turbo efficiency at 1.1bar of boost may suffer so it may fall short..

Who knows, its really only a guesstimate. Be sure to keep us updated.

[Cubes]

Depends how much $$ you can afford at the time.

A fuel pressure reg is only a couple hundred $$.

Purchase of the gtr injectors is around $300 and they generally don't come with the resistor pack. The resistor pack if you can find one second hand may be say $70 or so.. if not then bran new they are $160.

I wouldn't use second hand injectors that haven't been cleaned as you don't really know how well they have been cared for after they have been pulled out.

Thats another $20-25 each injectors, so worse case thats another $150.

300 + 150 + 160 worse case is around $600 + labour to fit them.

or ~$400-$450 + labour without cleaning them.

A fuel pressure reg is easy if you are only after a little more power that is only just out of reach.

[ScottKing GTS-4]

HPI ran an article on adjustable cam gears and found they made considerable advances on an RB20DET, especially the exhaust side by tuning it with a set of cam gears. What brand/spec cam gears are you running Roy? I'll see if I can find the article and get some info on their tune for you.

My cam gears resulted in a loss of power, and worse response:( Bloody RB25 owners you lot are a protected species with all those bolt ons meaning good gains:)

Im waiting for splitfires as well, then i can go back to 1.3-1.4bar and hope the adjusted clutch does the trick...fingers crossed. Your car would still leave mine for dead though on the street:thumbsup:

[ScottKing GTS-4]

Thanks for the info mate. What about a high pressue pump? This would also allow me to hit a bit more power that may be out of reach wouldn't it?

Depends how much $$ you can afford at the time.

A fuel pressure reg is only a couple hundred $$.

Purchase of the gtr injectors is around $300 and they generally don't come with the resistor pack. The resistor pack if you can find one second hand may be say $70 or so.. if not then bran new they are $160.

I wouldn't use second hand injectors that haven't been cleaned. Thats another $20-25 each injectors, so worse case thats another $150.

300 + 150 + 160 worse case is around $600 + labour to fit them.

A fuel pressure reg is easy if you are only after a little more power that is only just out of reach.

[Cubes]

Not sure if I'd rather fit a fuel pressure regulator or just fit a bigger fuel pump. Probably fit a bigger pump, out with the old in the new right.

Obviously depending on the dyno again but a bigger pump is still at the limit for the injectors. 200rwkw is getting close to lean territority should you have a slightly dirty injector or a fuel filter that is only a tinny little bit old.