Modifying the RB20DET for about 300hp

[dareo]

Few questions, i wanna go slightly bigger on injectors and turbo. Correct me where i'm wrong:

R32GTR injectors are direct drop in but require resistor pack (found where?)

Stock DSM 450cc injectors can also work (what mods required?)

370CC CA18DET Injectors can work, but need resistors as well.

Any T3 flanged turbo should fit (best to look for oil cooled only?)

Stock RB20DET turbo is safe/reliable to ? (i dont know yet)

SAFC+stock MAF+370-450cc injectors should get along well and produce~300hp with proper tuning. I'l probly get a Wideband and do my own real world road tuning.

Stock 240sx 5 speed driveshaft should work with 5 speed RB20DET and Tophat Mounts (like anyone will know this for sure yet)

I wanna just get enough power to have a good time with the car w/o spending a ton of money....as long as its faster than my friends 20 valve AE86 of course.

Confirmed Answers will be edited in for future reference, as i didnt find a much good info searching. Lets make this be a RB20DET Quick Reference guide.

[GTR Shop]

You can damn near get 300hp out of the car on std turbo and injs.Basically, more timing and pulling fuel out with tuning will get good results..

[Wulfgang]

I thought the standard injectors were only good for maybe 250 chp.

Also, do you really want to replace a water-cooled turbo with a non-water-cooled turbo? Because it's easier to install, or what? Why go backwards in reliability?

[Carl H]

std injectors are like 270cc.they are really small and will need to be replaced as 300 is well over the injector limit.also stay with watercooled turbos, last longer than oilcooled turbos.

[GTR Shop]

I work those injs out to be good for 325hp, and we make 300hp out the RB20s on std gear...

[goofynick6]

So you're saying 450cc dsm injectors would be plenty for 350whp? Because the 550cc price range is quite a bit higher, and I'm not sure if the safc can deal with them being more than 100% larger than stock.

Nick

[GTR Shop]

450cc injs are good for ~540hp..

[goofynick6]

Hmm...that seems really high according to about 10 of those online fuel calculators and stuff. Is that at stock fuel pressure or with a rising rate unit? I had 440's on my 2.5 V6 probe before when I turbo'd it and they were plenty, but I only ran 10 psi, I figured with higher boost and temps that 450's might not be enough for my goals, but if you say so, then I'd believe you since you have more experience with these engines.

Nick

[GTR Shop]

Yu can run 90hp per inj out of 450cc... 6x 90hp = 540hp

[goofynick6]

Where do you get that number from? Any calculations I've done using a b.s.f.c of .60 have said that in order to reach 450 crank HP, you'd need something along the lines of a 550cc injector running at 42psi and 80% duty cycle.

Not doubting what you know, just curious where you get the 90hp per injector number from.

Thanks,Nick

[Wulfgang]

I am doubting.

And for those stock injectors, several online calculators will tell you that even 250 hp is pushing it with stock fuel pressure.

[GTR Shop]

Goofy: For a start you have a base fuel pressure of ~42psi, you also have Xpsi boost to be added to that. so 10 psi boost, you have 52 psi.As a rule of thumb (which you will find listed online) devide cc by 5 to get hp per inj.. it works in real life, not online clacs.

Wulfgang: we made ~205hp atw on a Rb20 the other day at std boost with filter and exhaust. (151kw atw IIRC) (printout avail)That was acheived by a little more timing via the CAS as it was orginally retarded.The AFRs were in the 9s!! we have since pulled the mixtures out to 10.9-11 in the top end and it goes ALOT better... I mean ALOT! I'd expect it to be 165kw atw now... with more avail.This was done in experimentation with a OLD single dial Apexi AFC, 10% out (max for unit)Std pump, std fpr, std boost, std turbo..

If you run 8:1 AFR as I have seen from some factory Nissans with light mods, then you will make LESS power than 12:1 and also run higher duty cycles.

I know of vehicles running 380hp atw on 444cc injs.. on std fpr.600hp atw on 720cc injs at std fuel pressure running 1:1 boost compensation.Work that out on the (cc/5)x #cylinder forumla..

Another example was a RX7 I was tunign a few weeks back.. injs duty cycles were ~90%, and the owner was going to throw some bigger injs at it.Once tuned on the current injs, the car made about 15% more power and duty dropped to ~82% by pulling the mixtures from 8.8:1 up to 10.5:1... car was making 400rwph, now ~455 so effectily by getting the mixtures closer to what they should be, you have removed 10% of the existing duty on the injectors.

AFR has a BIG influence on duty cycle.I wouldn't look at upgrading any injs unless you KNOW 100% you have good AFR, and the duty is getting ~90% and you want to add more boost to it.

[Wulfgang]

Ok, I believe.

I checked out some info.... many of the online calculators use 0.5-0.6 lb/hr/hp bsfc, but I see some stuff that estimates modern cars get more like 0.42-048, which would support the numbers you gave.

Now I have another question. For that rb20, why did you just go to 10.9-11? Why not 12:1? Looks like you're making about 225 bhp, but isn't 11:1 still really crappy for stock boost?

Anyway, this whole discussion just makes me realize more how much I need a wideband and eprom emulator.

[GTR Shop]

WHy only 10.9-11?YOu may have missed the bit about old single knob AFC.. 10% was its max.I didn't even know I still had the thing! found it and installed on a mates car and went out with the wideband for a play to see what we could get out of it AF wise with the unit.

Hes selling the car hence why not going to a SAFC 2.Reason for sale: he has just brought a GENUINE 260RS Stagea Autech Version and doesn't need 5 other cars! yes hes Nissan Mad.. out of the 6 cars he owns, 5 are turbos, all are Nissans and ALL are modified!

Buy a LM-1 and a SAFC2 and go to it!

[goofynick6]

Hmm...I still dont' know if I'd feel safe with 450cc injectors to make ~350 whp, I feel like they might be at their limit. I might just spring for the 550's to be safe.

Although, I'm not sure if an SAFC2 would be able to control the injectors if they're that much larger than stock (going to run 300zx maf as well)

Nick

[WDRacing]

With a FMIC stock injectors 2mm head gasket for a lower CR and stock turbo, I was pushing 311 on the GTECH meter, I never dyno'd the car in that trim. But I have found the GTECH to be pretty close on the money with 1/4 times. I never did a dyno comparison, but even dyno's very from machine to machine.

I was also running 17 psi. I didn't have a wide band at the time, but did use a MSD Knock Meter, which never indicated knock at that boost. I was also running 100 octane gas though.

Think about alcohol injection.

WD

[goofynick6]

I want to maintain an easy to use/ street-drivable machine, so no kind of extra injection stuff for me....just 6 injectors.

I'd totally forgotten to calculate the extra fuel pressure added with boost, if the stock FPR adds 1 psi per 1 psi of boost, then at 15 psi, the pressure should be up to like 55 psi? I don't know what base fp is with a walbro 255 and the stock fpr. That amount of pressure would essentially turn a 450cc injector into a 520cc or so...hmmmm. More thinking to do.

Has anyone hooked up low impedence injectors with a resistor box on the rb20?

Nick

[Wulfgang]

...I'd totally forgotten to calculate the extra fuel pressure added with boost, if the stock FPR adds 1 psi per 1 psi of boost, then at 15 psi, the pressure should be up to like 55 psi? I don't know what base fp is with a walbro 255 and the stock fpr. That amount of pressure would essentially turn a 450cc injector into a 520cc or so...hmmmm. More thinking to do.

Nope. The purpose of the fpr is to maintain a constant pressure over the manifold pressure. So when your fuel rail pressure increases by 15 psi to 55 psi, then your manifold pressure also increased 15 psi, so the pressure DROP across the injectors stayed the same. Injector flowrates are specified for a specific pressure drop, not a rail pressure.

[goofynick6]

Ahh yes...I totally forgot that too! Sorry, been a little while since I've messed around with injector sizing and calculating, forgot that whole part..hehe.

So, 550cc RX7 injectors it is

Nick

[hannibal]

So how would you get a RB20 up to 300whp with stock turbo and injectors??Add downpipe, exhaust, intake, FMIC, up the boost, and tune the hell out of it??WD, did you push the stock turbo past 17psi w/o alcohol?

[GTR Shop]

Nope. The purpose of the fpr is to maintain a constant pressure over the manifold pressure. So when your fuel rail pressure increases by 15 psi to 55 psi, then your manifold pressure also increased 15 psi, so the pressure DROP across the injectors stayed the same. Injector flowrates are specified for a specific pressure drop, not a rail pressure.

NO.. inj flowrates are at a specific rail pressure and duty cycle.Most are flowed at 3bar, wide open. (free flow)A compensated reg is there so that under vacuum the rail pressure is lowered to a point that the ecu can give the inj small enough pulse widths and still maintain the correct fueling.Ever trying to set up a set of 800cc insjs on a 55psi fixed pressure (ie no comp)?? most ecus can't control pulse widths that small with that amount of fuel to get a even idle.. just too fat with mixture.

The other angle of the reg is to supply the fuel required under boost.. Flow the same inj at say 38psi (vac rail pressure) and 60psi (boosted rail pressure).

GOOFYNICK: ever seen a GTR make 350hp atw with std injs?? I have.. MANY times.. they are ~440ccI know of quote a few making 400+ rwhp on std injs..

[goofynick6]

Hmm, 400whp on 440cc's is probably about pushing it; I think I'll prefer a little more safey margin for the extra $100 or so, and that way I don't have to worry about upgrading if I want to run a few more psi at the track or something.

I did some calculations for the walbro 255, and at 50 psi, it can handle 570cc injectors, so it would be about as high as it could go.

Nick

[WDRacing]

The stock turbo is nothing but a heat pump after 17 psi. In fact, 1 Bar is about maxing them out. 17 is pushing the limits.

WD

[GTR Shop]

Why is it pushing it? 400hp atw is under 90% duty.. with the correct AFRs.

[Wulfgang]

NO.. inj flowrates are at a specific rail pressure and duty cycle.Most are flowed at 3bar, wide open. (free flow)A compensated reg is there so that under vacuum the rail pressure is lowered to a point that the ecu can give the inj small enough pulse widths and still maintain the correct fueling.Ever trying to set up a set of 800cc insjs on a 55psi fixed pressure (ie no comp)?? most ecus can't control pulse widths that small with that amount of fuel to get a even idle.. just too fat with mixture.

The other angle of the reg is to supply the fuel required under boost.. Flow the same inj at say 38psi (vac rail pressure) and 60psi (boosted rail pressure).

You said "NO," but you are saying the same thing. The regulator is there to provide a constant pressure drop from rail to manifold. That's it. Nothing more. If that pressure drop is usually 3 bar, then yes, the injector is rated for 3 bar (pressure drop) at 100% duty cycle.

So at idle, the deltaP is 3 bar and the manifold is close to -1 bar, so the rail is at 3-1=2 bar.

At 1 bar of boost, the deltaP is still 3 bar, the manifold is at 1 bar, so the rail is at 3+1=4 bar.

Simple. Anyway, I think everyone knows how injectors work so we don't need to get off topic and discuss that here... I was just reminding goofynick6.

[GTR Shop]

You said inj flowrates are rated at a specific pressure drop... and not rail pressure.

Well.. NO.. they aren't.. if you look at the spec sheets, they are 95% of the time rated at 3 bar (rail pressure) and wide open.

[GTR Shop]

BTW, std RB25, 12psi dropping to 10psi from 5000rpm onwards, 41psi base fuel pressure, exh/filter made 300rw hp at under 80% duty (actually 299.6hp)

[dareo]

that is some freaking sweet power on only 12-10 psi and stock fuel. The RB25DET is impressive, but also too much $$$ for me. I found an NX2000 and my compulsive car addiction insists i buy it and put in an SR20VE...in addition to the two RB20DET swaps i got planned.

*edit* I saw an Ebay auction for a supposedly stock RB20DET turbo and it had ceramic blades. Please confirm/deny the ceramic turbine blades in the RB20DET. If it has the ceramics by my logic it should be much more boost limited than 17psi.

[GTR Shop]

The power isn't anything flash.. just fuek tweaked with a S-AFC.. you'll also not the base fuel pressure is LOWER than factory.. this makes the tunig a bit easier as yo don't have as much to do as far as changes.

All 20/25s and 32/33 26s run ceramic turines.They fall of when over speed and heat cycled badly.They are effectivly glued onto the shaft.

[PsiloX]

http://homepages.tig.com.au/~robs/tuning.htm

Check this site out this guy made 350hp with the stock injectors and a t3 turbo.