Rb25det S13 Issues

[PSI-S12]

hey guys.

new on here, and exploring the worth of RB.

recently put an RB25DET S2 into my missus' Sil80, and having a few dramas after the swap.

firstly, the car dies at 5000rpm. feels like boost cut, and most probably is boost cut, but just getting a second opinion.

the car is running factory turbo but has had an external gate welded to the factory exhaust manifold (i know, right.).

assuming the spring in the wastegate is too big, its hitting more boost than it is capable of handling, and cutting out.

so the question is, what boost maximum can a factory motor handle? the ecu, injectors, AFM are all factory.

secondly, im having issues with rpm thru the speed range.

the car sits at 4500rpm at 100kph. and no its not the cluster, it is ACTUALLY sitting at 4500, screaming its tits off.

one would assume this would be a final drive ratio issue, but i had no problems while running an SR20, and this has an RB20 box behind it, which is more or less the same internally as an SR20 box, so it has me stumped.

last of all, this one might be a bit of a niche field for the RB powered S13 owners, but im trying to find out the best way to keep it cool?

i cant get AU falcon fans to fit between the engine and the radiator, so its got zero fan forced cooling.

only cooling mod that it has currently is an alloy radiator. which is defanitely not safe coming into summer haha.

any help or direction is appreciated!

cheers

Will.

[James_03]

What is it running off then the internal or external wastegate?

I am guessing the external gate, which is pretty useless if your running factory ECU still. The easy solution is simply run your vac line to the internal and leave the external disconnected. This will more than likely fix your boost cut issue as well.

You should be running 7~10psi to be safe but can go to 14.

Was it previously an auto? What gear are you sitting in that's pretty crucial info. For the cooling look at slimline thermo's, that's what a mate runs in his rb25/180. Just 2 of those without a shroud works fine.

[PSI-S12]

cheers for the reply man.

internal gate has been removed, and the flap welded shut.

if a factory turbo can see 14psi, i guess the spring in my gate must be WAY huge haha.

ill see if i can find another turbo and swap them over, get it running like factory again.

car has always been manual. i was obviously in 5th gear otherwise id feel like a douchebag posting this up haha.

ill have a hunt around for some slimline thermos, do u know what brand makes them?

cheers for the help man

Will.

[Dose Pipe Sutututu]

I used to own a RB S13, I can tell you one thing ditch the A/C condensor and the A/C system all in total. Run 2x 12" inch fans blowing into the radiator rather than a pull setup.

What you also can do it cut the radiator support to move the radiator forward if you want to keep your A/C setup.

I still had my full A/C setup, but it over heated quite easily under some load. I was running 1x14" fan pushing from the A/C condensor and 2x Craig Davies Slimline pulling from the Radiator. A total of 3x thermos to cool the sucker down!

An oil cooler will HELP heaps, I notice as soon as the oil temp reached around 100+ degrees, the water would start to climb like mad.

There's not much airflow in the engine bay due to lack of room, but if you really want the A/C system, I suggest cutting the radiator support and tilting the radiator forward so that you can fit 2x thermos behind it.

You will need to do some trimming as the fan will touch the water pump & the crank, I used a R32 GT-R radiator so I didn't need to cut my radiator support.

As for the rpm, get yourself a SR20 diff, their like 3.8:1 unlike the CA 4.3:1, or just slap on a S15 Helical 3.9:1 diff

[badhairdave]

secondly, im having issues with rpm thru the speed range.

the car sits at 4500rpm at 100kph. and no its not the cluster, it is ACTUALLY sitting at 4500, screaming its tits off.

one would assume this would be a final drive ratio issue, but i had no problems while running an SR20, and this has an RB20 box behind it, which is more or less the same internally as an SR20 box, so it has me stumped.

Have you corrected the tacho? If not it definitely is the cluster. Your ear tacho may be faulty

SR diff is 4.1, the car will be cruising at about 3k. your tacho is reading 50% high becasue of the extra ignition pulse per rotation of the engine so showing 4500. I've seen it more times than i can remember.

simple test. bang it off the limiter. factory rb25 limiter is around 6850 from memory, so with an sr tacho you'll be showing well off the scale (around 9.5k)

[Dose Pipe Sutututu]

are you using the stock cluster? if so it will be reading wrong.. you will need to splice a resistor with +ve inline OR use the R32 tacho... click on the link under my signature

[PSI-S12]

cheers for the replys guys.

johnnilicte, you didnt find the fans on the front of the rad were blocking the air flow at all?

im liking the idea of the GTR rad plus 2 fans pulling. i hope i have the room. AC can GTFO haha

not keen on the idea of the rad support chop, as its a street car and i dont really wanna risk being defrected for altering factory structural support.

oil cooler idea is mint too! will try and find a cheap kit.

with the RPM, the diff i have in the car is a 3.9:1. factory SR20DET. and all the people ive heard of doing the swap never had to alter the diff ratio.

the S15 diff is torsen, and torsen is one of my pet hates haha. so i think ill stick with an S13 diff, and just try putting a 3.7 in.

i honestly dont think my ear tacho is having problems its really high pitched, but will get a second opinion.

the wiring for the cluster has not been altered yet, but is def on the cards. will have a flip thru that wiring diagram when i get a chance, thanks heaps for that!

badhairdave, if i could bounce it off limiter, i would haha. but gotta fix the boost cut issue first!

i heard a tale today, that sometimes the knock sensors can be damaged during the swap, and can cause the engine to fail at higher RPM. your thoughts?

Will.

[blind_elk]

johnnilicte, you didnt find the fans on the front of the rad were blocking the air flow at all?

It won't matter which side of the radiator the fans are on (and ideally they should be mounted to PUSH air through the radiator), they are still covering the same area of radiator.

And you need to make sure that the air can't go anywhere other than THROUGH the radiator - a lot of the time, the air simply flows down the front of the radiator and goes under the car.

[slippylotion]

If your car was a FACTORY manual (remember some cars come over as manual but where auto from the factory) it will have a 4.08 ratio and the auto was a 3.9 ratio.

[Aiight]

i highly doubt you would actually see 4500rpm (or even close to that) at 100kmph in fifth with ANY factory diff.

i wouldnt stuff around with the diff until you get that tacho sorted.