Would You Use A Standard Rebuild For Light Motorsport ?

[Touge Kyousou]

Hey guys,

Seems i've lunched my 3rd engine lol, blown head gasket or something.. dumped coolant which was contaminated as hell, pop new coolant in and now coolant temp fluctuates, interesting a coolant dump and fill exposed an issue but anyways...

The car gets used at wakefield a bit so i'm thinking of instead of repairing whatever is wrong with it, to do a rebuild instead. Problem is i don't think i can really afford a forged build but a standard build will be ok. I will be speccing a better headgasket and arp bolts though.

What do you guys think of running a fresh standard build rb25 for circuit work ? I do treat the car very good in that i do about 2 flying laps then 2-3 cool down laps then 2 flying laps again so i'm not continuously leaning on it. Motor also gets fresh oil before a visit, and gets dumped straight after (have been using penrite hpr 10-50).

On the flying laps the car really does get pushed though, as i'm there solely to chase PBs.

Current setup in a nutshell:

260rwkw on e85, suspension and r comps.

As part of the new build/repair/replace etc, the turbo is getting swapped out for one of hypergears latest hi-flow, and i will be running the motor up to ~300 rwkw e85, however this high boost mode will probably only be used once in awhile e.g. drag (if i ever go lol), or maybe just one lap at wakefield for craps and giggles. I suspect majority of the time the car will be running in approx 260-270rwkw as that's how the rest of the car is geared for (brakes, tires etc).

tl;dr
do you think a standard rebuild with good HG and arp head bolts will survive moderate track usage on 260rwkw ? Plan is 6 track visits a year.

Cheers

[GOD12A]

Heya TOUGE,

Kinda different but same idea, I have a 26 with 340rwkw@20psi on 98.

Internally factory except the cams. I rebuilt it over christmas as she was pretty worn. Didn't bother boring the block as they were in tolerance, so I just had them honed, new rings, new bearings and a few reliability mods on the crank etc

I didn't have the money to step up to a forged bottom end knowing I'd definitely exploit the stronger bottom end and force myself to buy a bigger fuel system, big single snail, then clutch, then bigger cooler etc etc

So I stuck with OE bottom end purely to restrict my horsepower spending and redirect money to other areas to help reduce lap times and get racing (better shocks, half cage, new semis)

I think if you're mechanically sympathetic and have a decent engine builder (who can measure properly), stick with OE and build to OE spec (don't deck unless it's out of spec, don't bore unless you have to etc)

It'll keep money in your pocket for other go fast bits that'll make a direct difference to lap times

Mark

[89CAL]

Nothing wrong with a standard rebuild at those power levels, I'd add ARP main bolts as well as having the head bolts for a bit more piece of mind. They aren't that expensive anyway.

As long as the assembly is done right I'd be happy to run it. Especially seen as its quite a bit cheaper than a full forged rebuild. If you can afford the forged engine, then of course its going to be tougher, but probably not necessary

[scotty nm35]

MLS gasket and ARP's in the engine you have now is the best, most obvious option to me. No need for forgies till 400+ imo, as long as you stick to e85.

It's just a head gasket, and it probably wouldn't have happened if you had stuck the higher clamp force bolts in at the start... Manufacturers use stretchy bolts as a fuse against bottom end damage imo.

If you are bothering to rebuild it, I would probably replace the internals and lean on it harder, but that's me.

[GTSBoy]

On top of the sensible suggestions above....

If I were doing a build like that and not wanting to put forged stuff into it, I'd be looking at what I could do to help it handle heat and abuse. I'm really tempted by ceramic coating for insulation on the piston crowns, and ceramic coating for lubrication on the skirts. It's not too expensive, but you do need to keep its intended presence into mind when sizing stuff.

Other than that, a bloody good oil cooler setup, decent ducting and so one for the heat exchangers at the front of the car, attention to undertray and hot air escape.

[Touge Kyousou]

Hey guys,

Thanks so much for all the helpful replies Looks like i'll be going for a standard build then.. i really can't justify performing a forged build due to other commitments plus i know i don't want to lean on the motor past low 300rwkws with reasons being lack of traction, the new turbo purchased maxes out at 320rwkw on e85, wakefield doesn't exactly favour big power and also killing all the other parts quicker.. so if the standard with uprated bolts and gasket will handle it, i'll be happy to run that and have some change leftover to go to other stuff.

I'm probably going with autosport engineering at kirrawee for the build.. my last few visits have been good and have heard good stuff about them, plus the owner races nissans...

Roger on the cooling, am looking into oil cooler... i don't want one too big to add further weight up front especially past front axle line so maybe one of the smaller jjr kits. Car already has a 40mm alloy rad, cooling panel and raised bonnet. Will look at undertray too but i don't think i'll have space for ducting... was looking into putting front brake ducts which will take whatever's left of the space and the a/c is still intact too (and will remain)...so there's not much room ?

CHEERS

[Blackkers]

you got the R33 highflow from hypergear?

I have that turbo on e85. heaps of power in the top end unlike most other highflows. Toshi said it feels like an SS1pu but I wouldn't know

[Touge Kyousou]

Yeah just paid for it last night so don't actually have it yet, plus the motor needs to be rebuilt first so it'll be awhile before i feel the turbo. Stao sent me a dyno readout of the latest highflow and on e85, 22psi it put out 320rwkw but i'll only be running around 270rwkw (actuator pressure of 18psi) for a bunch of reasons posted above.

[jjman]

While of course motorsports does put higher levels of strain on a motor (and the RB25 are never a young motor anymore) Im a little curious how you are now through your 3rd motor.

What were the causes of the other failures?

Are you limiter bashing a lot? WOT shifting?

Is the radiator and fan in good condition (with shroud), is it a track tune (safer tune with more leniency). Can you tell what your knock levels, engine and oil temps were during use?

The reason I ask is that perhaps there is an element of mechanical sympathy you are overlooking that might be killing motors a little pre-emptively?

[Touge Kyousou]

jjman,

1st motor died through poor tune and hard street driving. 2nd motor died from a mech forgetting to replace a part, third (current motor) from track usage.
I've only just started track visits start of this year and have been 3 times. To be honest, i didn't expect this motor to last too long due to age and circuit usage..

Was loading on the current motor and car more and more after each visit including mods. Current tune on it was good, i told the tuner it was going to see track 6 times a year, so the car was detuned to 260rwkw and afr's were track friendly on e85.

Not much limiter bashing, only coming out of hairpin and last turn on wakefield is where it'll see some limiter bashing. Hairpin after a little limiter gets 3rd gear. Final turn is throttle modulation to avoid it. No WOT shifts, ever (you mean not releasing gas and shifting yes?)

I monitor knock and coolant temps through PFC hand controller. There is a fan shroud and fan appears to be working well.. i've never let the coolant reach high 90's, highest i've seen was 95 out of all 3 visits, that was at almost 3 laps.

Always open to suggestions

[GTSBoy]

When I said "ducting" I meant making sure that the cooling air all goes where it is supposed to. This means controlling leakage and flow around the sides of the intercooler and radiator primarily. But when fitting an oil cooler it means taking care to make sure that it gets a solid flow of cooling air through it so that it doesn't just hang in the breeze doing less than it might.

When I said "undertray" I mean the bit between the front of the lip/splitter and the radiator support panel (there's usually nothing there and there needs to be). And of course the factory undertray under the engine needs to be there.

It's all free cooling - needing only your time, a bit of thought and some effort (and some corflute and/or grey foam) to achieve.

[jjman]

jjman,

1st motor died through poor tune and hard street driving. 2nd motor died from a mech forgetting to replace a part, third (current motor) from track usage.

I've only just started track visits start of this year and have been 3 times. To be honest, i didn't expect this motor to last too long due to age and circuit usage..

Was loading on the current motor and car more and more after each visit including mods. Current tune on it was good, i told the tuner it was going to see track 6 times a year, so the car was detuned to 260rwkw and afr's were track friendly on e85.

Not much limiter bashing, only coming out of hairpin and last turn on wakefield is where it'll see some limiter bashing. Hairpin after a little limiter gets 3rd gear. Final turn is throttle modulation to avoid it. No WOT shifts, ever (you mean not releasing gas and shifting yes?)

I monitor knock and coolant temps through PFC hand controller. There is a fan shroud and fan appears to be working well.. i've never let the coolant reach high 90's, highest i've seen was 95 out of all 3 visits, that was at almost 3 laps.

Always open to suggestions

good man. you know what you are doing then.

this being the case my recommendation would be to find a stock motor with good compression and vitals etc and put that in after a good cooling system cleanout and also some decent head bolts. Its all a lot cheaper than a rebuild too... Stock RB25s are cheap as chips these days.

Also mean that if it goes bang you don't have to deal with the heartache of the $ and care that went into a rebuild.

otherwise, what manifold are you running?. the stock manifolds are known for their choke tendencies and heat building... Not a good thing for track work.

[scotty nm35]

otherwise, what manifold are you running?. the stock manifolds are known for their choke tendencies and heat building... Not a good thing for track work.

I have built multiple cars running stock plenum/airbox/manifold and made close to twice what OP is running. It isn't those choking anything, more likely the turbo (rear housing) selection or tune.

[Touge Kyousou]

GTSBoy,

Thanks for clarifying, i'll be sure to do what i can once i get the car back with regards to ducting then.

jjman,

Yes running stock manifold and don't really have the budget for a ffp and associated pipework =/. The build is already a small stretch haha.

I hear you on finding a factory motor.. that's what i thought when i had the 3rd motor installed.. been quoted 2-2.5 for repairing the BHG including machining...i'm thinking i may as well spend a few more k on top then have a built motor that i know is fresh. Am also wary of all the reports on SAU of people getting motors built only to be not done right needing another build =/

Scotty,

Correct, rear housing is choking hence the detune. This is why as part of the build i've already bought a new turbo and will be running that one at nowhere near it's max efficiency for trackwork. It will probably run close to max for a couple of runs at the drags IF i ever make it out there, but only because my mate with an fpv wants to race it down the 1/4.

I think the tune should be ok - from a reputable tuner in sydney and they race a silvia themselves.

Thanks all

P.s. looks like forged build at this shop is not much more than a standard build as they want to bore/deck for standard build and they already use ARP bits for even the standard build. So i guess i'll just have to stretch and go for the forged build, or repair whatever's wrong with the motor.

[scotty nm35]

Scotty,

Correct, rear housing is choking hence the detune.whatever's wrong with the motor.

Can a lack of timing be part of the issue? My manifold temp gets pretty hot on e85, and it spikes when i hit the soft limit... It also causes the boost to spike substantially. Do you log any of that data at the track?