rb20 w/rb25 turbo...sounds like backfiring!!!

[armysweitzer]

So i swapped out my blown 20 for a 25 turbo. Swap went well but near 10psi or at WOT the turbo seems like its losing power and sounds like its backfiring. I vacuum at 15 at idle ( warm engine) and 20 on decel. The turbo was in good shape with no shaft play or anything.

I was thinking boost leak cause it seems to smell really rich after it backfires but I couldnt find a obvious leak. The car really seems a lot slower but im assuming thats cause of whatever problem Im having...

RB20 s13. Stock minus exhaust.

[Bronze MFP]

so you're running a rb25 turbo on a stock rb20 engine, with no fuel upgrades or anything? 10psi on a rb25 turbo is flowing a lot more air than 10psi on a rb20 turbo, look into bigger injectors and a better fuel pump if you don't already have one. the stock rb20 fuel system is about maxed out with the stock turbo pushing 12-14psi, so i'd imagine the rb25 turbo is out of the stock fuel systems range.

[armysweitzer]

i thought about that, put if i accelerate slowly i can hit 10 psi smoothly without any backfiring or stuttering.

what injectors would I need (didnt need anything over 320hp) and would a safc be good enough till i upgraded more?

[Bronze MFP]

370 or 444cc injectors would do well, a safc would work, but if you could get your hands on a powerFC that would be better. what fuel pump are you using?

[BoostFab]

back-firing = running rich.seriously, the rb25 turbo isn't signifficantly different than the rb20's, other than the fact that 's newer. you're fine!!!!check your fuel pressure....and perhaps boost leak...etc..

[Yellow4g63]

I'll take boost leak too.

[armysweitzer]

ok cool, I knew i needed new injectors and what not but for some reason it just didnt seem to be that. I ll do a boost leak test tomorrow.

Also Would a FMIC kit see a decent amount of lag over the smic?

Reason for asking being my friend with a sr seemed to notice one in a butt dyno test.

[Wulfgang]

This is a fact: It has been shown that the RB20DET MAF/injectors/ECU are good to at least 296 rwhp with no tuning.

If you're already running rich, how could larger injectors possibly help????

[armysweitzer]

idk im stupid!

[klh6686]

have you checked the gap on the sparkplugs? you may need to set your gap from stock 1.1mm to .8mm. give that a try, bet it helps. good luck

[armysweitzer]

what plugs would you guys recommend, ive been meaning to swap new ones in but ive read a lot of things about different plugs and to be honest i didnt want to mess with it untill i got a solid recomendation. THanks so much for any help I wanna drop these in tomorrow!!!

-love newbie!

[rb20fb]

i am running a rb25 turbo on my 20 and i have no problem, i just swapped a stock ecu into my car and it runs great, all i have is a walboro 255lph and a tt 300zx fuel filter on mine, when i had the tomei tuned ecu in the car would shoot flames when i shifted at high rpms but that was it.

[armysweitzer]

hmm intresting, I cant wait to get in my garage tomorrow and find those damn boost leaks.

[Vkoslak]

my rb20det backfires under decelleration and sometimes when I shift gears. Even without the exhaust wheel.

[Cubes]

I would look at spark plug gap (set to 0.75mm, check coils for arcing why you are there) and boost leaks.

Don't waste money on injectors yet they are good for close to 300rwhp with a little fuel pressure. On the dyno I run on at least. :P

[armysweitzer]

yeah my number one cylinder's plug had broken off (the little curved end) Replaced em all, regapped and works a LOT better. Never knew how much better gas milage would be with all working cylinders.

Seems to still sputter a tad but i didnt even look for any boost leaks yet.

Thanks for all the help and responses guys!

[Valley]

have you checked timing? on my rb25 it didn't like to go above 6k rpm because the timing was off.

[sean8564]

I had the same problem on MY Rb25 when i put on A RB20 Waste gate to run more boost. also I have no exhaust at all

[BoostFab]

what plugs would you guys recommend, ive been meaning to swap new ones in but ive read a lot of things about different plugs and to be honest i didnt want to mess with it untill i got a solid recomendation. THanks so much for any help I wanna drop these in tomorrow!!!-love newbie!

i recommend NGK 3330 (BCPR7ES) gap to 0.8mm

[Carl H]

This is a fact: It has been shown that the RB20DET MAF/injectors/ECU are good to at least 296 rwhp with no tuning.

If you're already running rich, how could larger injectors possibly help????

gaaah!296rwhp is over 320 at the crank, and rb20 has 270cc injectors so its WAY over the max 100% duty at that point.maf yes, injectors no; fuel should be adressed on any rb20 that is going to be modded before anything else imho (well past basic bolt ons).

[armysweitzer]

i used denso 3008, the same as NKG R somethings or others. The car seems to be better it still does it sometimes, I really cant explain why/when/how it does it. It just does it when it feels like it.

PS wanted to hook up my speedo, simply plug it in?