Gt4294 On A Rb25?

[STATUS]

Just perused my dyno hall of fame and there are 9 car making over 500rwkw (670hp) the cheapest engine was around 20k, i have 5 out of that nine over 550rwkw (740hp) and i reckon all those engines owe at least 30-40k.

But in fairness we are talking wheel hp and Kw i find that in the states fly horspower seems to be the used currency and many use the pie in the sky 25% rule so 740hp fly would be 550rwhp or round abouts... this is only 410rwkw and is fairly easy to achieve and FAR cheaper.

We have seen a few 2.5litre cars roll through the shop making this power (400-430rwkw) with cheap GT4088 turbos with the special order v-band rears. Engines were simple home builds Pistons, rods and cams.

[PM-R33]

There you go, thanks for that

He did say "solid 700-750whp, maybe more" so i assumed he ment 500+kw@wheels. If he ment engine horsepower and was using a percentage conversion, than i take back what i said, however i still wouldn't be going cheap on the main ingredient in making power.

Edited December 2, 2009 by PM-R33

[Sean W]

you say tomayto, i say tomahto?

[KB240RB]

I havnt yet built the engine. I'm looking at all possibilities. Even if that means selling it for a small block chevy. Lol. Internal wise I will obviously use forged pistons and I beam rods. Acl race bearings. Polish and balance the crank. Balance the pistons and rods as well. Head wise I'll be going solid lifters and 270 cams. Also a port and polish job. My neighbor does my machine work for me and I do the assembling. Fuel system will be 96lb injectors, aeromotive a1000 fuel pump, sump tank, and aero fpr. Probably a -6 feed with -8 return. Haltech ps2000 ecu. Of course I'll have to pick up more parts along the way but these are my main parts I'm focusing on. There are many people in the states making big numbers on journal bearing turbos. There not junk at all.

[STATUS]

I havnt yet built the engine. I'm looking at all possibilities. Even if that means selling it for a small block chevy. Lol. Internal wise I will obviously use forged pistons and I beam rods. Acl race bearings. Polish and balance the crank. Balance the pistons and rods as well. Head wise I'll be going solid lifters and 270 cams. Also a port and polish job. My neighbor does my machine work for me and I do the assembling. Fuel system will be 96lb injectors, aeromotive a1000 fuel pump, sump tank, and aero fpr. Probably a -6 feed with -8 return. Haltech ps2000 ecu. Of course I'll have to pick up more parts along the way but these are my main parts I'm focusing on. There are many people in the states making big numbers on journal bearing turbos. There not junk at all.

Dismiss the journal / BBearing debate on here, its a moot point and irrellevant.

i build a few V8's too and can tell you a "real" 700hp sbc is gonna cost you 25k at least.

this is a genuine 550+ rwkw engine and is worth over 30k

Edited December 2, 2009 by URAS

[Cjmartz2k]

Dismiss the journal / BBearing debate on here, its a moot point and irrellevant.

Well, at least there is one thing in this thread I can agree with.

OP--I'm not going to get into the "aussie hp vs american hp" debate again, although I think you should clarify if you mean rwhp or motor hp. We do for the most part talk about rwhp on this board and most others now actually. I will say admitting you don't already have an assembled engine and your pockets aren't exactly lined with cash, you might want to knock out building your engine before you dream about what turbo to buy. I think saying you need to spend $30-$40k on an engine (especially an LSX) to get 700rwhp is a bit mellow dramatic, but people LOVE to throw money at stuff on here, so take it for what it's worth. I'm not going to push my turbo choice too hard since everybody needs to make up their own mind, but I will say considering you budget, the fact that you are in the states, and hp goals, you should for sure look into the Holset HX52 (the holset thread I created would be a good starting point) as Lithium mentioned earlier in the thread. I think it would be an excellent fit for what you are looking to do.

[KB240RB]

I'm not gonna get into an engine debate. I've built a high power engine before for nowhere close to what your saying. Let's focus on the turbo at hand. If you dont have experience with it then please don't post.

[KB240RB]

I'm talking whp that's backed up with weight and trap speed. I don't buy into dyno numbers unless it's proven by a run down the track even if it's not for a good et.

[Lithium]

OK so you'd be looking for a setup capable of getting an S14 down the 1/4 mile trapping around 145mph?

[STATUS]

Well, at least there is one thing in this thread I can agree with.

OP--I'm not going to get into the "aussie hp vs american hp" debate again, although I think you should clarify if you mean rwhp or motor hp. We do for the most part talk about rwhp on this board and most others now actually. I will say admitting you don't already have an assembled engine and your pockets aren't exactly lined with cash, you might want to knock out building your engine before you dream about what turbo to buy. I think saying you need to spend $30-$40k on an engine (especially an LSX) to get 700rwhp is a bit mellow dramatic, but people LOVE to throw money at stuff on here, so take it for what it's worth. I'm not going to push my turbo choice too hard since everybody needs to make up their own mind, but I will say considering you budget, the fact that you are in the states, and hp goals, you should for sure look into the Holset HX52 (the holset thread I created would be a good starting point) as Lithium mentioned earlier in the thread. I think it would be an excellent fit for what you are looking to do.

i should also add i dont consider LS engines to be traditional SBC's LS's make power easy, 700hp from a traditional SBC is an expensive execise. Decent alloy head setup alone is 5k.... roller cam kit 2.5k... rotating assy 2.5k we are already @ 10k no rocker gear, sump , pump, ignition, carb etc....

[KB240RB]

Like 145+mph if you figure the car weighs 3200lbs stock trim including a full tank of gas and me. Back on topic, when do you guys think a 70mm turbo will hit full boost on a rb25?

Edited December 3, 2009 by KB240RB

[Cjmartz2k]

Ahh, okay. That makes more sense. I still think you can do it with an old 350 based engine for cheaper then what you mentioned, but there certainly is a substantial jump up in challenge/price when you try it with a pre-LSX series motor.

[KB240RB]

I could do a sbc pretty easily here in the states. I can get all those parts you mentioned for half or a 1/4 of the price you mentioned. A high compression e85 carb setup would make alot of power. Especially if I would use a dart block and do a 4xx stroker. Majority of the power is in the heads. Spend 2k on a set of 18* heads and itll have plenty of flow. A solid lifter flat tapet cam would do the job too. I would definitly use nitrous though just to be sure I make the numbers or more. The problem with a v8 like that is crappy driveability with the carb. Guess I could always do a efi setup on the engine. Skys the limits with a sbc here in the states. I could do a new generation lm7 with lq4 aluminum heads and do a custom front mount turbo setup. Those engines stock handle 700-750whp with a solid tune. Alot of guys here are doing that through automatics. So almost 900hp at the crank. I can get the lm7 for 400$ and the heads for 200$. Then spend around 2k on a fuel system and around 3k on making my own turbo setup. A few hundred in new gaskets and such. Another 500 or so on good valve springs and a cam. A budget build on a v8 is possible.

[Lithium]

Like 145+mph if you figure the car weighs 3200lbs stock trim including a full tank of gas and me. Back on topic, when do you guys think a 70mm turbo will hit full boost on a rb25?

I'd be expecting mid/high 5000rpm range, though might be wiser to check with the RB26 brigade as it would be incredible similar - strangely enough

[Rolls]

You seem very hung up on a peak power figure but you say you want it to be daily driven, 1/4 etc. Now unless you get a custom diff ratio and gearset (or auto with a massive 5k stally) so you never leave the power band 500hp on a 4L motor is going to feel twice as fast as 800hp on a 2.5L motor.

Have you considered spending the money on going to a larger capacity motor such a a 3L or something totally different to a RB motor? The reason I ask is if you went to a 3L+ motor you wouldn't have to spin the motor as hard, you would have less lag and hence wouldn't have problems keeping it in the power band with standard diff and gear ratios.

You said you had 600hp on an s13, I am going to assume you meant the 4 banger because you didn't say otherwise, now this 'wasn't enough' as you said. Now if you measure the average power, or the area under the curve of your useable revs you will probably find that a strong 4-500hp 3L build will make a dickload more usable power than a 750hp 2.5L and will feel far faster and be faster on the street. This is because you constantly have to keep it between 7000-8500rpm so that you are actually making any power, not to mention the terrible throttle response.

edit: You mentioned you would consider using a V8 (I am going to assume at least 5L or greater in capacity) now this is WORLDS apart from a 750hp 2.5L i6, the average power will be almost DOUBLE on the v8 due to not having to rev its ring out all day to get it on boost.

I would very seriously consider looking at a 3L block as a minimum if you want to make this sort of power and have it useable. Also do not use a plain bearing turbo, that is just going to make the problem (horrible horrible lag) even worse.

Edited December 3, 2009 by Rolls

[KB240RB]

600hp was on a SR20 with 67mm turbo. It was laggy. Very peaky powerband but it felt great to me. Had the economy of a 2.0L during normal driving but hauled ass at WOT which is all i want the power for. That turbo was full boost around 5500rpm and less tq than a 2.5 would have. I used it for street racing and the only cars around here that could stand with it would be a drag v8. But even then it was only cause they could dead hook off the line using a auto with trans brake. On the highway it was a different story. Was running with 1L bikes majority of the time. It had quite the reputation till i sold the engine back in September. I built that setup for $15k. Thats including the cost of the motor set, building it, different clutches used, tunes, gaskets, little odds and ends like that. Doing the work yourself saves a ton of money.

I totally understand the concept of cubic inches and tq making for a way more responsive setup. In regards to that, I already having the RB fitted into the car, id like to use the platform. I believe in keeping things simple and using the parts internally to handle the power needs. Use the turbo thats gonna meet my flow requirements (doesnt have to be the bees knees, just something that works the way its made to). A proper MAP standalone for tuning. And a proper fuel system. Im not against using nitrous either for spool up if i would get into racing again. For now i just like a fast jaunt every now and then down the highway.

From my understanding with the Journal Bearing and Ball Bearing turbos is the biggest difference being the transient response between shifts. Itll take a second longer to build boost again because of the journal bearing drags the speed of the wheel down during the shift. From what ive seen comparing 67mm journal and ball bearing turbos is not a large difference in spool time at all. Maybe 200rpm. Its just the response during shifts. Im not too worried about that. Once again im not out to win races at the moment. If i were into competing id definitly look at spending the money on a BB unit for the edge.

The Rb30 block is a PITA to find in the states. People overprice them horribly. Id switch to a 2jz before doing that.

I can deal with mid to upper 5000rpm for full boost. Currently ive got a 4.36 rear in my car and will be using a 26x10.5 tire. If revving out to 8500rpm, its got enough gear to reach 150mph in 4th gear. Thats perfect for the trap speed i hope to hit. Ive often thought about going auto but doing so i would need nitrous without a doubt. Sorry if i may have said daily driven. Itll be street driven. Not more than 100-150 miles a week. Weekend warrior for the most part. No sense on putting a shit ton of miles on a built motor.

Edited December 3, 2009 by KB240RB

[SimonR32]

dropping boost between gear changes is more to do with a driver than the type of bearings in the turbo

[STATUS]

I could do a sbc pretty easily here in the states. I can get all those parts you mentioned for half or a 1/4 of the price you mentioned. A high compression e85 carb setup would make alot of power. Especially if I would use a dart block and do a 4xx stroker. Majority of the power is in the heads. Spend 2k on a set of 18* heads and itll have plenty of flow. A solid lifter flat tapet cam would do the job too. I would definitly use nitrous though just to be sure I make the numbers or more. The problem with a v8 like that is crappy driveability with the carb. Guess I could always do a efi setup on the engine. Skys the limits with a sbc here in the states. I could do a new generation lm7 with lq4 aluminum heads and do a custom front mount turbo setup. Those engines stock handle 700-750whp with a solid tune. Alot of guys here are doing that through automatics. So almost 900hp at the crank. I can get the lm7 for 400$ and the heads for 200$. Then spend around 2k on a fuel system and around 3k on making my own turbo setup. A few hundred in new gaskets and such. Another 500 or so on good valve springs and a cam. A budget build on a v8 is possible.

but here nitrous is cheating.... we are all talking pump gas no nitrous.

[KB240RB]

lol. I dont know what weiiand blowers cost over there but there between 2-3k for like a 8-71 here. That would easily get it over 700hp. You could then go a little cheaper in the heads and still make the power. Personally i like turbo power better but doing a blow through carb setup drives horrible from what ive been told. Supposably its super lean on anything other than WOT.

Edited December 3, 2009 by KB240RB

[Lithium]

dropping boost between gear changes is more to do with a driver than the type of bearings in the turbo

The bearings can make quite the difference with Garrett BB vs plain bearing turbos, people get hung up on where full boost is hit between BB and plain bearing turbos when under full load on the dyno... you don't see the true effect under controlled acceleration against a dyno, its when you stand on the gas midway through the revrange that it becomes truly noticeable. I know a few people who have had T3T4/T67/T04R type turbos which on shifts etc they have to really rape them to keep them on song, change to a BB equivalent and the car feels almost electric by comparison.