The First 400 whp
Ok, so one of the key things I learned in this process the hard way is that there is a very clear lines in the stages of the NSX engine. Now it isn’t a magical HP number or anything like that but there are clear points in which really distinguish one stage of the car to the next. I think generally people accept that around 400-425 whp is around the limit of where you can push the stock engine. And up to that power level, I still feel the NSX is essentially the same car, just with more power. The balance is slightly off, but I think you can get to that level of power without having to change or modify too many aspects of the car that really change the “soul” and feeling of the car. And I think it is possible to maintain the reliability and drivability of the car that is close to stock levels to a degree.
But as I said, there are no guarantees. I wasn’t so lucky. Well when I first got my car, I dyno’d at a whopping 239 whp. At the time the car was the fastest thing I had ever been in and it was a blast. After a few years, I got very accustomed to the speed and my test drive in a Factor X turbo car (putting about 450 whp) was simply intoxicating. The rush of the boost was just too much to pass up. My first thought was that 400 whp would be MORE than enough to satisfy my speed lust (oh how naïve I was!) so I looked into building a turbo kit for a nice 400 whp or so. Also I didn’t want to jump into a 550 whp monster and wrap myself around a tree. It was my understanding that 400 whp was considered “safe” on a stock engine so I didn’t need to worry about the cost of building the engine. I was on a budget so I wanted to minimize costs. A compression and leak down test came out positive so I felt I had nothing to worry about. However, knowing I was starting to push the limits of the car I did anticipate that I something could happen. I wanted to push that 400 whp and keep pushing it until something failed. Then I would go ahead and fix that or build the engine.
I made it to about 405 whp when I lifted a head gasket a spewed oil everywhere. That’s not really blowing up my engine (I consider that .5) but I did have to take the car back to the shop and pull the engine all over again. At the time, I thought about building the engine then since I was pulling the engine, but since I was in that “magic” range, I thought I would be ok. I made it up to around 425 when one I crushed one of my piston heads. Hard to say if it was a tuning issue or just fatigue on the engine. My car had around 135,000 miles on it, so it didn’t really surprise me. The piston head didn’t have any real indications of detonation (burnt oil, high temp marks etc.) so I don’t know.
500 whp and Beyond
So that was the perfect time to build a race engine. Basically I upgraded the pistons, rods, sleeved the engine, upgraded the motor mounts and throttle body. I didn’t go for the full build yet, cams, valves, springs etc, because at the time I really thought there would be no way I would go beyond 450-500 whp. Now the thing I learned was this incremental increase in power was an exponential increase in cost. Once you throw in the engine build, it really starts to add up the cost of the build. Also this was where I upgraded the clutch because the stock clutch was showing signs of high temperature glazing and slippage. I went with an RPS stage 1 clutch, which in hindsight was a bit short sided because I would end up replacing it in a less than a year. The other thing I learned was that once you break down your car to that level it will never quite feel the same. When I got my ’91, even though it had 130K+ miles on it, it was still pretty clean, nice and solid. You really got a feel of how solid the car was and how clean it felt. But once you start stripping down the car, it’s very hard to maintain that fresh OEM feeling. Things tend to squeak or rattle or crack. The car just feels just less put together. It’s hard to describe, but anybody who has done extensive work to any car knows that once you start to just strip it down it all starts to feel more race-carish and less refined. Things just don’t feel as tight. Dirt and grime gets into odd nooks and crannies that a car straight from the factory just doesn’t have. You might have a slight oil leak, or extra grime coming out of the exhaust. You might get more fuel smell or funny idles. The car may stall and leave you stranded. It’s not any one thing I can single out. Once you get to around the 500+ whp mark, you’ll start to have to incorporate fundamental changes to the NSX that just start to transform it into a different car. Like I said in another post, for example, to be able to keep up with 500+whp, you’ll need to upgrade to something like 1,000+ cc fuel injectors. Those are huge because they need to be sized to flood the bejesus out of the engine with fuel for wide open throttle. But think about it, just how good do you think 1,000+ cc fuel injectors are going to be at idle or partial throttle (which is 95% of the time). Not great. It's like trying to water your plants with a fire hose. These are things you don’t have to do at 400 whp. But these are changes you have to make at 500 whp and will change how your car sounds, how it wants to idle, and how clean the junk is coming out from your tail pipes. A lot of the times I can tell a high HP NSX simply because it just has a rough start, very coarse and unrefined idle, and there are dirt and oil marks on the back bumper above the exhaust ports. That’s stuff you don’t have to deal with on a stock engine or even 400 whp. Another thing to note is at 400 whp, depending on your tires, you will have a hard time maintaining traction, especially in the first couple of gears. So do you think adding another 100 whp will be realized in the form of a faster car? No, not really. All you’ll get is even MORE wheel spin. So once you get to that level of power, you need to think about upgrading the wheels, suspension and brakes. Otherwise, adding all that power is wasted in just short tire life span. The main problem is that on a stock body, generally speaking it is hard to get wider than 295 wide rear tires. And at 500 whp, even that isn’t even enough. I had to go wide body, partly for the looks, but partly so I could stick fatter 305 wide tires in the back. Not to mention, that the stock NSX tire sizes are very well matched and balanced. Meaning, the amount of rubber on the front tires is balanced to the amount of rubber on the rear (balanced ratio). But once you start dumping some serious power to the rear tires, you’ll start to realize that all you care about is more and more rubber on the rear tires because otherwise, it’s like your rear tires are on roller skates every time you jab the throttle. The problem is that you can go up to 295 wide in the rear and even up to 305 in some cases, but it is very hard to get past 235 wide front tires without significant rubbing. That means the ratio of the widths of the front tires relative to the rear becomes wildly out of balance. The car will feel and handle completely different. As I mentioned above, the NSX starts to lose that original stock/OEM NSX feel that you were used to. Often times people expect an NSX at 500 whp to be just like their stock NSX only with just more power. It’s not. You have to be prepared that you’ve created an all new vehicle using an NSX shell. It still is a uniquely NSX experience but it’s just not that super clean, super refined, super honed, super balanced car the stock NSX is.
The other thing I learned is that once I started pushing past 500 whp, you really start to open up all the other avenues of where links on the chain really start to break down. After 500 whp, things like trannys, clutches (again), axels, cams, differential, etc. start to show their weaknesses. And because there are so few players in this market at that power level, the costs really start to exponentially add up. Also at this point, you’ll start to realize you NSX has less OEM parts on it than aftermarket parts. Once I hit 500 whp, the car felt fast again, but it wasn’t long before again, 500 whp felt slow. Previously I had only built up the rods, pistons and sleeves, so I knew that I’d be pushing the limits of the engine again by increasing the power. Again, I slowly increased the power until the engine blew again. This time I think I was around 550 whp. But this gave me the chance to redo everything properly. I redid the entire engine (new block, sleeves, rods, pistons, etc.) but also upgraded all of the ancillary equipment such as valves, LMA, springs, throttle body, etc. Also upgraded the clutch to the RPS stage II twin disc clutch because the old RPS wasn’t handling it. The next tune was putting me at around 600 whp and I had it there for a while unit the engine blew one more time. This time more catastrophically; one of the cylinders/piston head melted and basically ruined the block. This one was a bit more unexpected and I realized that at around 600 whp I was really starting to push the limits of the next threshold in the engine and turbo. I was basically maxing out the turbo and I would have to upgrade more things on the NSX to get it to run more reliably at the 600+ whp level. At that point, I felt that the NSX was turning more into a purpose built vehicle instead of the balanced street cruiser/race car I wanted it to be. So I rebuilt the engine one more time, upgraded the axels, rebuilt and upgraded the tranny, upgraded the limited slip differential, and multiple other things. The plan was to bulletproof the engine (i.e. beef up all of the links in the chains) and detune the car down to something more stable at 550 whp and have something I felt was powerful enough, yet reliable as I can make it. So far the car has been pretty flawless and as close to a stock experience as I can make it. No oil leaks, stable throttle response, no idle issues, etc. Only time will truly tell if this latest configuration will last, but I’m hoping by pushing the car to its current set up’s limits, then backing off a few degrees, I’ve set up a reliable build.
Con't
