technical questions

[Ferraripilot]

For you engineering types and technical hobbyists (like me), I have some questions regarding this engine:

Piston deck height and quench distance? I see the pent-roof style combustion chamber is very efficent in these, but what sort of total ignition timing do these run and with what is the quench distance (distance from the piston deck to the head deck)? On most engines, the idea is to have a .040 quench but I am not so sure regarding these engines.

Regarding ignition timing, what is total timing? 32-34 degrees-ish? Or does the knock system in place constantly change total timing according to weather/fuel quality etc.

Head flow. I would guess at least 140-150cfm at the intake average is no big deal with these, but again I don't know and I am interested in doing some mapping with an engine building program I use. Also, was the exhaust tuned to flow 80% of the intake or was Honda just not there yet with that sort of flow engineering? I bet they were....

 

[Honcho]

For you engineering types and technical hobbyists (like me), I have some questions regarding this engine:

Piston deck height and quench distance? I see the pent-roof style combustion chamber is very efficent in these, but what sort of total ignition timing do these run and with what is the quench distance (distance from the piston deck to the head deck)? On most engines, the idea is to have a .040 quench but I am not so sure regarding these engines.

Stock gasket thickness is 0.030. All of the NSX techs I have ever spoken to have advised not to mess with the stock quench and deck height on the NSX engine. If you do change the deck height, you need to use these because the centerline of the cams will change relative to the crank and your timing will be off otherwise.

Regarding ignition timing, what is total timing? 32-34 degrees-ish? Or does the knock system in place constantly change total timing according to weather/fuel quality etc.

The NSX PGM-FI system has a knock sensor and adjusts total timing on the fly in real time. Factory timing is set at 15 deg (+/- 2 deg) BTDC at 800 rpm on a manual transmission NSX. Total timing is set at the factory and the adjuster screw is covered by a rivited block, meaning Honda does not want you touching the timing adjuster. There is a procedure to do so involving drilling out the rivets to remove the block and expose the adjustment screw, but only to get the timing back to OEM spec.

Head flow. I would guess at least 140-150cfm at the intake average is no big deal with these, but again I don't know and I am interested in doing some mapping with an engine building program I use. Also, was the exhaust tuned to flow 80% of the intake or was Honda just not there yet with that sort of flow engineering? I bet they were....

I am sure some people have had NSX heads on a flow bench, but no one has ever disclosed the numbers. Here is the bottom line: the stock heads flow extremely well from the factory. 3.0 and 3.2 engines with even modified cams show little gain with head work. You should PM member greenberet- he has a lot of info and insight on the breathing capability of the stock engine. The stock airbox provides far more CFM than the 3.0 or 3.2 need to run at max efficiency. In fact, the SPEED World Challenge NSX used the stock airbox with a supercharger.

The bottleneck in the intake is the bellows and throttle body, but at 3.0 liters there is no restriction and only a slight one (worth maybe 5 hp) at 3.2 liters. It's only when you add FI or increase displacement that you really start to see a problem. On stock engines, things like bored throttle bodies and extrude honed intakes add only small amounts of power. Honda designed this engine to flow well. The real "flow" bottleneck on a 3.0 is the exhaust. The manifolds are cast iron and restrictive and the exhaust is too. Headers and exhaust make a big difference on the 3.0 (20 whp or more). The 3.2 comes with OEM tube headers, so the gain is not as great.

Honda took everything they knew from Formula 1 and poured it into the NSX engine. The flow was designed and tested using Honda's F1 facilities. It has long been accepted that finding NA power on the NSX is very difficult and expensive. It's a big reason why Comptech ditched their NA engine program and started selling the supercharger. Bang for the buck. That's not to say NA power is impossible. The C32B used in the JGTC NSX race car is basically a stroked (3.5) verson of the stock NA2 engine with hot cams, ITB and Motec engine management. It makes 500+ hp. Closer to Earth, Vance's NA2 dynoed over 300 whp with just headers and exhaust. I personally think a NA NSX is the way to go and if you have the money, go for it!

 

[Ferraripilot]

Great response. You pretty much hit everything I was looking for.

NA engine building is sort of a hobby of mine as I much prefer it over any forced induction option. I found the ITBs and the other NA options which yield gains and they of course look fantastic.

I find it interesting that total timing is set by a screw of all things. Bosch had the sense with their motronic units in essentially making timing unadjustable unless the chip was changed, but I suppose there are benefits to both paradigms.

300rwbhp from 3.5L is not bad at all. A stock 355 typically rear wheel dynos at about 310-320 but the torque is just not there. A friend of mine owns Nick's Forza Ferrari website and his personal car is a bored 3.5L 2 valve 308 engine which makes exactly 300rwbhp with 260lbs tq and is a street motor. Don't ask what it cost! I suppose the same can be said for any high end NA build although some are more horrid to do than others. Nice to know Honda obviously has an excellent base to do this stuff with.

 

[Honcho]

Great response. You pretty much hit everything I was looking for.

NA engine building is sort of a hobby of mine as I much prefer it over any forced induction option. I found the ITBs and the other NA options which yield gains and they of course look fantastic.

I find it interesting that total timing is set by a screw of all things. Bosch had the sense with their motronic units in essentially making timing unadjustable unless the chip was changed, but I suppose there are benefits to both paradigms.

300rwbhp from 3.5L is not bad at all. A stock 355 typically rear wheel dynos at about 310-320 but the torque is just not there. A friend of mine owns Nick's Forza Ferrari website and his personal car is a bored 3.5L 2 valve 308 engine which makes exactly 300rwbhp with 260lbs tq and is a street motor. Don't ask what it cost! I suppose the same can be said for any high end NA build although some are more horrid to do than others. Nice to know Honda obviously has an excellent base to do this stuff with.

It is really a recessed knob unit (potentiometer?) that can be turned with a flat head screwdriver. The unit plugs into the PGM-FI system via a wire harness. So I guess it's not really a screw- Honda just calls it that in the shop manual.

Vance's 300 whp was from a stock 3.2 with headers and exhaust. That's the highest number I've ever seen and while I do believe it, I think it is rare. Most 3.0 engines dyno between 250 and 270 at the wheels with H/E. 3.2 typically does 270 to 290. The NSX engine was blueprinted from the factory, but even so, variances of 20 hp or more have been seen between engines.

The more I work on and study the C30A engine, the more impressed I am with Honda's engineering. In it's time it really was one of the finest engines in the world.

 

[A.S. Motorsport]

The more I work on and study the C30A engine, the more impressed I am with Honda's engineering. In it's time it really was one of the finest engines in the world.

Most definitely by far the one of the best engines ever designed.
I love C-Series Honda the new J-Series Honda is also very impressive and has huge tuning capacity with impeccable reliability.


Interesting to see the Ferrari guy's looking into the NSX engines
We work a lot with Italian sports cars, really makes you realize how superior Honda engineering is.