Hey guys, it looks like my car decided that it didn't want to keep up proper oil presure after about 39K miles and alot of hard use; so the engine has starting making bad noises. It looks like my winter project is going to be rebuilding the engine.

I do alot of track days (road course stuff) and the car has seen some pretty hard use. I am hoping to get some input from people who have strokers and upgraded turbos about thier experiences. Cars with big cams and ported heads (and even oversized valves) are especially relevant; we needed to port the intake maifold to match the intake runners on my car's head.

I am looking to find a tough stroker kit and big turbo combination that will make good power from about 4000 to 8000+ RPMs and be able to take the abuse a few years. I would prefer something that could survive 9K RPMs, but will probably never see revs that high. I have been considering the AMD 2.3 and Bushur Racing 2.4 kits and am hoping to possibly match that with a GT35R of some kind.

The car must be able to perform on well on 92 octane gas without needing race gas. Methanol injection is out (for now) - there could be times when it wouldn't pass tech if an inspector spotted it.

Please only post if you build engines or own a car with a stroker; "Brand X is best" posts aren't going give me the depth I'm looking for here. Thanks in advance!

 

You do of course realize you have yet to ask a specific question, having made only statements.

 

You already know the answer there are no negatives to going stroker except cost and even that is minimal. I had a 2.4 Magnus stroker in my old DSM and it was great. The extra TQ was noticable and full boost at 4K with a FP Red was good. I ended up selling the car.

There are no negatives just go with a premier builder. I personally would go with Buschur if for no other reason because of turn around times and reliability. Search for Al's post at the shootout and see how he went to 8900rpms in a stroker and had a nitrous backfire and she just kept on kicking and this was running 40 psi on a GT40 turbo!!

Good look the combo is proven you just have to fork over the cash!

 

You might want to talk to John Mueller (he's been fielding a 2.3l 3071 IIRC) and Smogrunner (he runs an AMS 2.3l 35r). Somewhere in the Vishnu forum I posted a comparison dyno chart with my built 2.0 3071 vs a 3037 (3076) vs Smoggy's setup.

Also, IMO, no kit is "going to take the abuse for a few years" ...

l8r)

 

I know what the basic benefits of going with a stroker are, no mysteries there. I'm also aware that no engine set-up is going to last forever when a car sees alot of hard use - my car was very well maintained and still failed. I would be a bit disappointed if I went through a rebuild and the engine only made it another couple of years though; Id like to see three times the life the OEM engine managed.

The reliability isssue is huge one for me. At a typical track day, my car may well see 4+ hours on the track going all out, even allowing for fuel stops, lunch, etc. I need to know the engne will hold up to that for at least a few years. While the car won't be my primary driver, in the summer I like to drive the Evo so it will see reasonable street use.

I guess I'm looking for some feedback about power delivery, turbo spool-up, secondary issues that have come up, things to look out for, etc. I have until late April or so (long MN winters...) before I'll be able to really drive the car, so I have plenty of time for research.

 

Sometimes the application demands more of an engine than it can provide, no matter how well the engine is maintained. They have to match.

How many race miles did your OEM engine last?

How often do you head out to the track? You need to quantify desired service life in race miles.

 

The other problem is simple... a stock motor was designed to take x amount of power for x time. Obvisouly the motor is capable of much more (As many of us have proven) but the point is the more you extract the more likely it is to fail... look at full on race cars. If thier motors last for a year they are happy Otherwise try to design yourself a thousand HP motor and detune it t around 500... Then it will probably last closey to what the stocker should I suppose

 

*sigh* I know that if I beat on the car it's going to break, but there are quite a few other cars (non-Evos) making big power in the crowd I play with that don't break. I'm ok with failures, but I was hoping to get some constructive feedback about set-ups that are less likely to break. Locally it looks like every Evo who's breaking about 300 whp (Mustang dyno) is eventually breaking...

Thinking of the engine's life in "race miles" is exactly what I want to avoid. I'm completely ok with that in a real race car, but not for the Evo. For me the Evo should be a fairly reliable track-day toy and summer cruiser. I'm also not looking for outragous power, and I am willing to detune a bit to get better life out of the engine. I'm hoping to see about 500 whp out of a stroker with the right turbo on 92 pump without methanol. I'm hoping to find a combo that can deliver that and last a while.

 

A target race mile service interval does not mean the engine cannot operate on the street. Transport street miles are insignificant compared to race miles so are not looked at. Race mile service interval is simply for quantification of target. Without quantification, all is lost in subjectivity.

If you are heading out to the track every weekend, tracking for 4 hours at a high speed road course, covering say 330 race miles in the process - that comes out to 1300 race miles a month, 15,500 race miles a year. Sorry but no high specific output engine is going to last even half a year . I don't mean it will immediately catastrophically fail, but that performance will degrade quickly (spring pressure, leakdown, friction-heat) to the point that if it is not rebuilt yet still operated like new, it will wear itself out very quickly and then blow up. Consider that in a 24 hour endurance race, about 2000 - 3000 miles are covered.
Compare this figure to what you are demanding of the engine.

 

FWIW, I would not be chasing big power in a road course vehicle without ensuring that I am at least in the 97th percentile in terms of laptime for the close setup. If I were you I would go 2.4, machined and assembled by a proven road race company, aim for 400 awhp or less.. low as 350 awhp at as low an RPM and wide a band as possible, spend on making all thermals are under control, and in the end have an engine and car combination that is repeatable and reliable in all weather, spend money on data acquisition, and learn how to interpret the data, and keep improving.

At power levels that high, laptime returns rapidly diminish and become less repeatable as power becomes peakier. Wear on the engine and other areas of the car also rises exponentially. Not worth chasing unless you are in real racing or have lots of money laying about.

 

IMO 500whp on pump gas is very optimistic, even for a 2.3l + 35r. If I was in your shoes, and going by my experience with my built 2.0l so far, I would give serious consideration to a 2.3/2.4l mated to a GT3071 turbo (or 3076 if you want to push it). Pump gas will just not be able to fully utilize the potential of the 35r. Just make sure the kit can easily be upgraded/downgraded to any GT series turbo between the 3071 and 35r series. That way if you change your mind about the turbo, it won't cost a small fortune to swap out.

l8r)

 

Thanks Ludi - Your suggestions hit pretty close to what my digging seems to be showing. While the GT35R (or RL) might give good peaks I am concerned about the overall power and delivery.

That said, I'm also concerned about having a turbo that's too small to keep up with the head and cams that are in the car; the current top end is heavily modified with oversized valves, insane porting (I needed to modify the intake manifold runners to match the head), and big cams. The Piper Rally cams I'm using seemed to out flow the HKS 280s I tested by a noticable bit on the stock (10.5 hotside) turbo; I expect the difference will grow with increased capacity in both flow and engine volume.

Currently I'm leaning towards the 2.3 set-up because of the lower piston velocities and lower than stock compression. I had figured that 500 whp might be optimistic, but I can always hope. I would probably be happy with anything over 450 whp; anything under 425 whp would feel very disappointing to me for the money & effort expended. I guess I still need to do more research on turbo set-ups.

Shaun - I'm familiar with "fixing the driver" first, but at this point I'm looking to get the car to where I can play with the very fastest of my crowd. In general I do tend to be near the top of the pack. The cars I'm chasing are generally on slicks with alot of suspension development and/or have a much better power to weight ratio - and most are also generally either dedicated race cars or super cars. Slicks (instead of my current R compounds) should help quite a bit in the corners and braking zones, but I still need more power for the long, fast straights.

 

I still think you're on the wrong track with the WHP goal. I think the real goal should be a certain level of torque, maintained flat across a range of maybe 3000 rpms, then tapering off. If you do the math, this type of torque curve matches up very well with the stock gearing. So ideally you'd want full boost at or before 3500 rpms, and have it start to taper off around 6500 rpms. If we're talking a stroker engine, then I'd guess that it will be able to spool up a 3076 to hit full boost by 3500 rpms, and with your setup on pump gas you should be able to hold a relatively flat torque curve until 6500 or so.

In my case I actually want my torque curve to be a little bit flatter than it is now, since it would push my shift point(s) from ~8200 rpms up to ~8500 rpms, but with a stroker engine, it would work out fairly well as is. Now, having said that, my torque begins to fall off around 6500 rpms (3071 on a 2.0). Comparing the theoretical airflow between a 2.3l and a 2.0l, I'd expect the 3071 to start falling off around 5600 rpms, so again a 3076 is probably the better choice in your case.

l8r)

 

I think you're thinking in "peak" terms here. Don't forget a 2.3 is going to be a torque monster. Even if it's "just" 425 awhp, you're going to have it a lot sooner.

 

Reving to 8900 on a 2.4 on a regular basis is not a good thing. Once in a while may be okay but its something you couldnt do everyday for extended periods of time.