So, I just got a promotion, and rather than go out and buy a Porsche, I'm thinking of the following-

I haven't seen much discussion on the forums about this, so I thought I'd ask the experienced engine builders about my hope for a higher revving VQ running medium boost. My goal is 500 rear wheel horsepower with as much torque as I can get at that power level across as broad an RPM range as possible, and run up to 8k RPMs. I also want to be able to daily drive the car without too much worry about excessive wear (within reason, obviously an 8000 RPM engine will wear out faster than a 6600 RPM one).

My ideas on the subject:

Darton Sleeved VQ35DE block so I can bore to 100mm (3.8L)
GTM Forged Connecting Rods
Arias Forged pistons @ 9.0 or 9.5 CR (see below)
Nismo Crank and Oil pump
Cosworth Heads
Either stock or upgraded cams (see below)
Cometic Head gasket
ARP L19 Studs
APS Twin Turbo kit, Plenum, Fuel upgrades, etc. (see below)
Turbo XS UTEC engine management

All of these components have been rated to 8000+RPM and medium to high boost. So on to the questions:

1 - What else do I need to pay attention to when thinking of high RPMs?
2 - I've read that the Arias Extreme Duty pistons need higher cylinder wall clearances, and since I don't plan on running high boost levels (only aiming for 500WHP, 600 crank), should I stick with the regular Arias forged pistons? Is the higher clearance and initial slop of the extreme pistons going to cause additional wear on the engine, especially for short trips? Also, would it be better to go with the slightly higher compression ratio to maintain low end power and torque given the power levels I'm looking to hit?
3 - I've read that cams for a turbo setup shouldn't be too aggressive, especially in overlap, because of backflow due to the higher backpressure of the turbos themselves. The stock cams are probably the least overlap cams I'll find. Stick with them, or go to high lift/longer duration cams to get more torque sooner and ignore/tune around the backflow issue at higher RPMs?
4 - Which Garrett turbos are used in the APS TT kit? I looked at the Mitsu turbos that come in the Greddy kit and the compressor map for them looks really good at the boost and flow levels I'm talking about (High flow at 8k RPMs on a relatively low 1.5 - 2.0 pressure ratio) but I like the APS TT kit better overall. Just want to make sure I'd get the same or better turbo efficiency.
5 - What power levels can I realistically expect on 91 octane pump gas, and what octane will I need to run to hit my power goals? Obviously results here will vary, just looking for guesstimates.

So, please, feel free to tear apart my misconceptions, offer advice, or just point and laugh!

-E

 

1: Not exactly sure why you would need a nismo crank...
2: You will need upgraded cam and cam accessories
3: forged pistons in general need high clearances. if it was me i would stick to the extreme pistons.
4. Backpressure is bad for F/I so stick with non agressive cams
As for your power goals I think you should be able to reach 500. I have the greddy kit so i cant say for sure about the APS. But sounds like thats gonna be one hell of a setup! Keep us posted!

 

You might want to wait to look into the new cams JWT is coming out with......basically you don't want something with a lot of overlap for boost, but something with some good lift.

as for the turbos, I think the stock APS turbos might run out of breath beyond the stock rev limit. I don't know this for sure but that's the impression I get from the size. The greddys won't spool as fast but they are a little larger and mitsu turbos tend to flow well up top.

 

Several reasons for the Nimso crank really. I'm considering doing all this on a brand new block, no core exchanges, so I'll have to buy a new crank anyway, and the Nismo crank is supposed to be stronger than the stock and lower stirring resistance so higher RPMs more easily.

-E

 

Keep in mind a couple of things.

1. 500whp in a Z is pretty damn eazy now and all you really need to do to the motor for reliably are rods, pistons, and ARP hardware.
2. You mention you want max torque and max rpm. The parts that yield high rpm will themselves sacrafice low end torque.

Given that, you could get the JWTT kit, with a built short block and make 500rwhp all day long at 12psi or so. The JWTT seems to be the torque king of all the kits out there, so it should fit your needs. No need to go overkill with sleeves, cranks, cosworth heads, etc. unless your goals are really far above 500whp

 

Cant see why, turbos are regulated by gas flow not engine speed. Its not like a supercharger where you can overdrive them.

 

uh huh, and if you've ever run a smaller turbo on a higher revving motor, you'll understand what I'm talking about. say an 8krpm SR20 using a T25. The t25 simply runs out of breath up top, you're spinning it beyond its efficiency range, it's not making any more power. There is no endless pull on turbos, if you rev a motor sky high, you can easily fall out of the efficiency range of the turbo.

 

Yup, turbo efficiency is one of my major concerns, finding something that will work at low pressure and high flow may be tough. That's why I'm so curious which turbos APS uses in their kits - if they have something that matches or beats the low side of the Greddy Mitsu turbo compressor map, that would work.

I don't see how high RPM modifications will be necessarily opposed to high torque. Most high RPM modifications are basically strengthening of the valve train, rods and crank, careful balancing, etc. None of these would hurt or help torque in my mind.

Increasing the displacement from 3.5L to 3.8L can only help torque, and lowering my compression ratio and putting restrictive turbos in are both going to lower my torque especially down low in the RPM range, and that's why I asked my question about the compression ratio. But I can't believe that high RPMs and high torque are diametrically opposed. I think keeping high torque from the 3k-8k RPM range will just be careful cam, timing, and compression choices, as well as making sure I have a turbo that won't be gasping for breath up there.

-E

 

Nobody knows which Garrett turbos APS uses?

-E

 

Believe its a hybrid they had built based on the GT35, a search will dig up alot of threads on this topic. Believe APS answered this on the other channel.

 

8k rpm is hard to do as far as i know... i once read a thread on a guy doing a n/a build up. his car reved up to 8.5k or 8k but he ran in to some problems getting to that rang. i think he was from austrailia

 

How much torque are you looking for? It sounds to me like you should be looking into the JWT kit. It is phenomenal! The numbers on my car are 504 and 567trq. That is at 12.5 pounds. If you want some more info on it shoot me a PM and we can talk about it.

 

Your going to need the Tomei 268's in order to rev that high. I dont think the S1 cams will work.

 

Basically, the volumetric efficiency of the motor far exceeds the smaller turbos output.

If you're referring to the actual exhaust gases driving the turbo then it is more dependant on the thermal expansion of those gasses rather than velocity of the exhaust. Hence, you see boost when a load is placed on the motor.

 

-EL,
What is your goal for running 8k RPM??

My suggestion is:
Keep the RPM's at stock levels or maybe 7100 if you're going with an off the shelf system. Now if you're going with an extemely large turbo like a T72 or something like that then high RPM's on a turbo car is warranted.

With what you have listed you're really opening up this motors breathing ability and you'll soon find out that the turbos can't keep up (as mentioned above). Also you'll see 500WHP & peak torque way before 8k and this would be the RPM band you'd want to keep the motor running in. Anything after that on these smaller turbos is a waste, power wise, with the mods you listed.

If you're hell bent on 8k I'd suggest picking up a SC kit, preferably a T-trim (like booger). You can control overspeed simply by adjusting pulley sizes.

 

I want the motor to be good for a broad range of tasks - track/autocross/very spirited daily driver. Not a drag racer or dyno queen though. A flat torque range across a very broad RPM band means less shifting, especially on autocross with all the usual tight turns of those courses. I realize I'll hit 500 horsepower long before 8k, that's the whole point... to hit my torque/power goals fairly early, and then use the UTEC to maintain them across a really broad RPM range by careful tuning of boost. If I'm sitting at 4 grand or 7 grand and I get into it, I'll get up and go, and will pull well all the way through the normal driving range. Is this a bad idea/goal? What is the downside, other than the cost and engineering challenges?

I'm fairly set on a turbo install, but I'd listen to really good reasons for a SC instead. I don't think there are any though.

 

Like I said, shoot me a Pm and I will help you with this, I also sent you a PM this morning with my phone number.

 

I got your contact info, thanks! I'll give you a call sometime and we can talk it over. I am still interested in a range of opinions though!

 

OK, so I did some searching and researching and I did find the earlier thread on the APS TT kit using GT2871R turbos. There was a lot of discussion as to if this is really the one included in the kit, but I'm going to hope and assume that it is. If so, the turbos should be fine to push enough Lbs of air for 8000 RPMs at 600 crank horsepower (figuring 15% losses or so for ~500WHP).

I think it'll also require the upgraded extreme performance fuel system due to the short duty cycles at the higher RPMs.

Getting warmer! Please, keep the suggestions flowing, I appreciate all the positive and negative input.

 

EL,
Going with an aftermarket cam like the tomei 268 will be beneficial for your goal of a high revving motor that makes power until redline...to safely get to 8000rpm, you are right in wanting to go with some built heads... (may I suggest the GTM heads-CNC port and polished, Ferrea 1mm oversized valves- will get flow charts scanned asap and emailed, pm me your e-mail address)...
Also, instead of spending the money on a different crank, I recommend going with a knife-edged crank to allow for a quicker climb in the powerband.

As far as the Pistons, go with the Arias Extreme Duty all the way, much more resistant to detonation, and if you are going to be tracking this thing (road coarse, I presume) and holding it at high rpm's for prolonged periods, you'll want to be extra cautious in preventing detonation... (also adding a form of water injection/meth injection)
Stick with 9:1 compression ratio, you'll have more than enough power down low with the increased displacement of the 3.8L (100mm pistons) and you'll be plenty safe when under full boost

pm sent

TODD