3.6L ScienceofSpeed Engine (NA Stroker)

greenberet · 22 June 2011

Wow! Those ITBs got you an 11% increase in rwhp plus an 8% increase in rwtq. I can’t wait to see the dyno charts to see where the gains are. That’s awesome.

Edit: if my wind and rolling resistance calculations are correct, then

if a stock NA1 5-speed’s engine puts out 235 rwhp at about 7200 rpm on a dyno and can push the car to 270 km/h (168 mph),
then an engine that puts out 369 rwhp at 7700 rpm on the same dyno on the same day should be able to push the car to 315 km/h (196 mph) if mated to a 6-speed transmission.

And with a bit of aerodynamic work you might be able to find an additional 4 mph. It would be sweet if a naturally-aspirated 3.6 liter NSX could hit 200 mph!

naaman · 13 July 2011

All this time I've been wondering how the 3.6 would stack up against the 3.8, and whether there were performance advantages to using the same stroke with smaller bore (faster moving pistons maybe?).

The 296 lb.ft at the wheels is very impressive. It must really pull hard.

BATMANs · 13 July 2011

does anyone have any hard data that stroking an engine essentially reduces the redline of the NSX engine?

also, i just dun feel comfy boring engines. I like to have as much sidewall materials to handle the combustion events.

Honcho · 14 July 2011

The big issue is piston speed and piston slap. SOS has done a great job of laying out the pitson and rod orientation so that speed increase is minimal. The chart comparing to OEM piston speed is on their site. Therefore, I would be comfortable with 8000 rpm on a SOS stroker crank and reliability would probably be about the same as Honda factory.

I agree that boring the OEM sleeves is a bad idea. You need a certain thickness of metal to maintain the integrity of the cylinders from both a thermal and structural standpoint. In fact, the service manual only recommends over-boring the cylinders a few thousandths. However, if you use aftermarket sleeves like Darton or Benson's, they are designed to use a larger bore with stronger cylinder walls than OEM.

I am also curious about the power differences between the 3.4, 3.6 and 3.8. stroker options.

3.4 = NA1 OEM bore (90.5mm) + stroker crank

3.6 = NA2 OEM bore (93mm) + stroker crank

3.8 = Max bore (95mm) + stroker crank

BATMANs said:
does anyone have any hard data that stroking an engine essentially reduces the redline of the NSX engine?

also, i just dun feel comfy boring engines. I like to have as much sidewall materials to handle the combustion events.

TANTO · 14 July 2011

Honcho said:
SOS has done a great job of laying out the pitson and rod orientation so that speed increase is minimal.

Not to denegrate the SOS work, but i'm confused as to this statement. I perhaps have not fully thought this out, but the stroke itself locks in piston speed. The strokers i have built (not nsx) used std length rods and pistons that were shorter from pin to top by the stroke amount. Perhaps you could run a shorter rod and taller piston. That would change the side loads which are THE concern on any stroker. Is that what you meant? Of course SOS determines the skirt length which affects the side load, but they don't have much leeway i would guess. You mentioned slap which results from the additional side load. Aside from air flow limitations, this additional side load is why most stroker motors (again non-nsx) LOWER their max rpm. This keeps the loads in an acceptable range. I understand that when a vendor tells his customers to expect piston slap to occur earlier and to not expect anywhere near normal piston/cylinder life unless he lowers red line, he loses business. But from my experience with v8's and bikes, you almost have to lower the redline somewhat. Problem with us nsx'rs is of course, we love our rpm. But in real life, strokers life is pretty short. You probably lose 2/3rds of life depending on stroke length. I would guess 30-50k max and perhaps much much less. The 3.8 length is just too long. Don't get me wrong, i plan to build probably a 3.5/3.6 myself, but my eyes are wide open. Strokers are one expensive proposition as they have to be rebuilt so often. And if/when you throw that rod and lose your crank and block, you have to have the attitude of "oh well, i was walking the line". And piston expansion vs cyl clearance becomes critical. All this is generally perfected thru miles and miles of racing. We don't have that avenue to exploit. Another issue is your tolerance for a noisy engine. Piston slap, which will likely occur is VERY irritating on a street car. Strokers are usually rebuilt not for loss of power, of from going bang, but from the loud slap that just drives you nuts. Please educate if i'm all wet. Love this thread.

Aaron94T · 14 July 2011

TANTO said:
Not to denegrate the SOS work, but i'm confused as to this statement. I perhaps have not fully thought this out, but the stroke itself locks in piston speed. The strokers i have built (not nsx) used std length rods and pistons that were shorter from pin to top by the stroke amount. Perhaps you could run a shorter rod and taller piston. That would change the side loads which are THE concern on any stroker. Is that what you meant? Of course SOS determines the skirt length which affects the side load, but they don't have much leeway i would guess. You mentioned slap which results from the additional side load. Aside from air flow limitations, this additional side load is why most stroker motors (again non-nsx) LOWER their max rpm. This keeps the loads in an acceptable range. I understand that when a vendor tells his customers to expect piston slap to occur earlier and to not expect anywhere near normal piston/cylinder life unless he lowers red line, he loses business. But from my experience with v8's and bikes, you almost have to lower the redline somewhat. Problem with us nsx'rs is of course, we love our rpm. But in real life, strokers life is pretty short. You probably lose 2/3rds of life depending on stroke length. I would guess 30-50k max and perhaps much much less. The 3.8 length is just too long. Don't get me wrong, i plan to build probably a 3.5/3.6 myself, but my eyes are wide open. Strokers are one expensive proposition as they have to be rebuilt so often. And if/when you throw that rod and lose your crank and block, you have to have the attitude of "oh well, i was walking the line". And piston expansion vs cyl clearance becomes critical. All this is generally perfected thru miles and miles of racing. We don't have that avenue to exploit. Another issue is your tolerance for a noisy engine. Piston slap, which will likely occur is VERY irritating on a street car. Strokers are usually rebuilt not for loss of power, of from going bang, but from the loud slap that just drives you nuts. Please educate if i'm all wet. Love this thread.

This is some great insight and some practical technical detail that is not often seen here, thanks for posting. I have never heard the reduction in engine life by 2/3 just due to the increased side load by a smaller piston. If that is the case why would you personally, even consider a stroker on your NSX versus just a CT supercharger?

Ponyboy · 14 July 2011

Stroker side wall data 3.0 vs. 3.8 (originally provided by greenberet)

FWIW, I have never experienced piston slap in my engine. However, I do get it in my sc'ed Yukon until it warms up.

greenberet · 14 July 2011

As a note, the side wall loading of Ponyboy’s stroker engine is less than is shown in the charts above. The charts assume that the wrist pins are located along the pistons' centerlines. After I uploaded those charts, Chris from SoS posted that they use pistons that offset the wrist pins slightly to one side, reducing the maximum angle between the wrist pin and the crankshaft and therefore causing less of an increase in side wall loading. If anyone knows how much the wrist pins in SoS’s 93 mm pistons are offset and can confirm that the wrist pins in the stock pistons are not offset, I could redo the charts. But I expect Ponyboy’s increase in side wall loading is below 13.9%.

TANTO said:
... in real life, strokers life is pretty short. You probably lose 2/3rds of life depending on stroke length.

In your experience, is bore wear proportional to side wall loading? Would increasing the side wall loading by 13.9% really reduce an engine’s life by 66% if you keep everything else the same (piston, cylinder, rpm, etc.)?

artek · 14 July 2011

Ponyboy said:
Stroker side wall data 3.0 vs. 3.8 (originally provided by greenberet)

FWIW, I have never experienced piston slap in my engine. However, I do get it in my sc'ed Yukon until it warms up.

im sure that has more to do with GMC engineering/tolerances than anything else =)

BATMANs · 14 July 2011

Ponyboy said:
Stroker side wall data 3.0 vs. 3.8 (originally provided by greenberet)

FWIW, I have never experienced piston slap in my engine. However, I do get it in my sc'ed Yukon until it warms up.

Now, that's information that I was seeking.

Usually i don't hear about piston slap in OEM cast pistons or most OEM forged pistons.

It's when folks (like myself) use the 2618 forged piston with the greatest amount of aluminum content that one can hear piston slap until the car warms up where the piston "expands into place".

Honcho · 14 July 2011

TANTO said:
Not to denegrate the SOS work, but i'm confused as to this statement. I perhaps have not fully thought this out, but the stroke itself locks in piston speed. The strokers i have built (not nsx) used std length rods and pistons that were shorter from pin to top by the stroke amount. Perhaps you could run a shorter rod and taller piston. That would change the side loads which are THE concern on any stroker. Is that what you meant?

As greenberet mentions, I meant the offset wrist pin. Strangely though, the SOS 88mm crank is no longer on their site and now there is a 86mm?

TANTO said:
The 3.8 length is just too long.

The stroke length on all SOS applications is 88mm. The differences in displacement are the result of different bore sizes. the 3.8 uses a 88mm stroke with a 95mm bore.

TANTO said:
Don't get me wrong, i plan to build probably a 3.5/3.6 myself, but my eyes are wide open. Strokers are one expensive proposition as they have to be rebuilt so often. And if/when you throw that rod and lose your crank and block, you have to have the attitude of "oh well, i was walking the line".

I agree with you and think you have the right attitude about this. Any time you modify an engine beyond OEM specs, you are gambling.

TANTO said:
And piston expansion vs cyl clearance becomes critical. All this is generally perfected thru miles and miles of racing. We don't have that avenue to exploit.

Actually we do. Honda raced a 3.5L stroker in GT 500 for years, which uses a Toda 84mm crankshaft. They used an OEM C32B block and IIRC, rpm was 9000+. Since they never changed the design and continued to use it year after year, I assume their race data confirmed it was a safe option.

TANTO said:
Another issue is your tolerance for a noisy engine. Piston slap, which will likely occur is VERY irritating on a street car. Strokers are usually rebuilt not for loss of power, of from going bang, but from the loud slap that just drives you nuts. Please educate if i'm all wet. Love this thread.

I think this is true for a Chevy 350 or Ford 302 block, but the C30A and C32B NSX engines were designed with a vastly superior tolerance and set up for 8000 rpm operation with a typical Honda safety margin. I don't think any of the stroked NSXs out there have experienced any slap noise issues. Ponyboy?

BATMANs · 14 July 2011

Honcho said:
......I think this is true for a Chevy 350 or Ford 302 block, but the C30A and C32B NSX engines were designed with a vastly superior tolerance and set up for 8000 rpm operation with a typical Honda safety margin.

Oh yea?

TANTO · 14 July 2011

Aaron94T said:
This is some great insight and some practical technical detail that is not often seen here, thanks for posting. I have never heard the reduction in engine life by 2/3 just due to the increased side load by a smaller piston. If that is the case why would you personally, even consider a stroker on your NSX versus just a CT supercharger?

Generallities are always a problem. My experience has been with go kart, bike and smallblocks way back in the 60-80's, all forged pistons but didn't even know or care about the material back then, and i don't even remember tolerances, etc. The smaller engines didn't last for shit, say around 5k for a motorcycle engine that would normally get around 30k. FWIW my mentors were national class racers, not hacks. Since the NSX is so high rpm, i would expect our engine to be in the same league as a bike engine, but it could be better. SB chevy 383's for instance have a very long life, but i suspect we are dealing with very slow piston speeds there.
Why consider a stroker? I wish i didn't have to, the costs give me huge heartburn. I wish we had a larger honda engine to build up and swap in (dream on). I'm 99% street. IMO if you track or street race, you HAVE to go FI. Sorry, but a stroker would be stupid for the track (unless rules dictate) But on the street i like a peaky engine like the F cars with a great and loud note. On the street the rpm's and the sound ARE a big issue for me. Riding high rpm bikes for years makes a differece perhaps. A super fills out the power curve which is great for racing, but makes the car feel like a low powered small block chevy and sounds too muffled. The parasitic loss drives my crazy on the street. Feels like you have the emergency brake on, again sorry to those owners. Fast but not fun on the street. I grew up with the SB, they are great engines, but they lack the effortless high rpm's the NSX and F-cars bring to the table. Just my tastes. Not many out there that put rpm and sound above ultimate power. And the latest turbo's are drawing my attention. IMO 500 HP is not worth the FI hassle. 600 plus is getting to where it may be worth it. But i beleive a conservatively built stroker would be the sweet spot, full well knowing it's a whole lot of money for a car that will still not be all that fast. I am targeting a car weight of around 2675. Power and speed are all relative. A 500 hp 3000 lb nsx is not all that fast either. Sorry for the ramble. Love this thread.

TANTO · 14 July 2011

greenberet said:
In your experience, is bore wear proportional to side wall loading? Would increasing the side wall loading by 13.9% really reduce an engine’s life by 66% if you keep everything else the same (piston, cylinder, rpm, etc.)?

Great question. One that i'm not experienced enough to answer. One reason i'm throwing out my verbage is to hopefully get others with more exerience to come out. My recollection pulling down stroker engines was that the piston skirt scuffing was getting to the point where too much metal was being worn away, causing the slap. I don't recall excessive cylinder wear, it was all pistons. I doubt piston material changes have actually changed much. Airplane technology developed piston designs in the early 1900's. While certainly worthwhile, i doubt the latest coatings do very much. We have to be skeptical of piston mfgr's "latest design" unless we have empiirical evidence. Another point is that the increased sidewall load causes a change in the resonance of the crank, and every other major component i would think. If we were working with a non-splayed crank run of the mill engine, i would expect 14% increased side load would be not problem. The push the envelope nsx engine with splayed crank makes us have to think twice about this. Crank thread to follow.

TANTO · 14 July 2011

Honcho said:
Actually we do. Honda raced a 3.5L stroker in GT 500 for years, which uses a Toda 84mm crankshaft. They used an OEM C32B block and IIRC, rpm was 9000+. Since they never changed the design and continued to use it year after year, I assume their race data confirmed it was a safe option.?

Well this is likely the wholy grail for us with stroker interest. I apologize as i've been absent from the lists for many years. What do we know for sure about this engine?. Internal details are so hard to get the straight scoop on, especially a racing engine. I remember several times comptech would state or infer a detail and then when talking with Shad or another mechanic and they would say something else. Saying the engine is "little changed" from stock is the stock line and can't be trusted. Honda not treaking every little part just a little bit? Hard to believe. They want you to think your car is "almost" a race car. Yeah right. And of course all racing engines are usually in some sort of trial. In this case though and knowing Honda, ALL the answers we seek are well known to one of two folks at Honda. Did you guys that went to the 20th anniversary take notes? I assume not. Asking folks you admire their secrets and tolerances in not really cool. I used to go around to races and ask details and take pictures. They always thought i was some kind of spy and wanted to punch me out, not that the Japanese gentleman would do that. We are lucky we have Shad. I suspect he has much of the Honda knowledge. And SOS is obviously coming on strong.

Ponyboy · 14 July 2011

BATMANs said:
Now, that's information that I was seeking.

Usually i don't hear about piston slap in OEM cast pistons or most OEM forged pistons.

Glad I could help. BTW, you forgot to mention your FD or GTO.

Piston slap is actually fairly common in GM 5.3 engines. Makes it sound like my diesel at startup. But it's lasted 180k so far - 100k supercharged.

Honcho said:
Ponyboy?

Nope, no piston slap. And I'd be honest enough to mention it as well.

I'm also going to respectfully disagree on a stroker for the track being "stupid." The engines power characteristics are perfectly suited for a track car - especially a Honda. And now even more so with the ITBs.

Honcho · 14 July 2011

TANTO said:
Well this is likely the wholy grail for us with stroker interest. I apologize as i've been absent from the lists for many years. What do we know for sure about this engine?. Internal details are so hard to get the straight scoop on, especially a racing engine. I remember several times comptech would state or infer a detail and then when talking with Shad or another mechanic and they would say something else. Saying the engine is "little changed" from stock is the stock line and can't be trusted. Honda not treaking every little part just a little bit? Hard to believe. They want you to think your car is "almost" a race car. Yeah right. And of course all racing engines are usually in some sort of trial. In this case though and knowing Honda, ALL the answers we seek are well known to one of two folks at Honda. Did you guys that went to the 20th anniversary take notes? I assume not. Asking folks you admire their secrets and tolerances in not really cool. I used to go around to races and ask details and take pictures. They always thought i was some kind of spy and wanted to punch me out, not that the Japanese gentleman would do that. We are lucky we have Shad. I suspect he has much of the Honda knowledge. And SOS is obviously coming on strong.

The Super GT (former JGTC) NSX engine was a stock C32B modified for race duty and served from 2000-2003. Most of the internal components can be found on Toda's website, where they call the engine package "C35B". Output in race trim (100RON race fuel) is 500 hp. The grocery list:

C32B Block
C32B Heads with titanium valve springs and lightweight valves, bronze guides
ITB Intake with roof snorkel
84mm Stroker Forged Crankshaft
Lightweight forged pistons
High Lift Cams
Adjustable Cam Gears
Dry Sump Oil System
MoTeC engine management

Toda also sells the C35B as a crate engine for Japanese race teams.

Ponyboy · 14 July 2011

For discussion purposes, Comptech even made a 3.9L stroker for use in a Daytona Prototype.

I'm sure this wasn't meant for a track car though.

naaman · 15 July 2011

So how many stroker engines are out there, and how many miles have the accumulated since the install? Any tear downs after a few thousand miles to asses whether wear and tear has increased?

greenberet · 15 July 2011

TANTO said:
While certainly worthwhile, i doubt the latest coatings do very much.

Coatings have improved a lot since the NSX was introduced. For example, diamond-like carbon (DLC) coatings have been developed with extremely low wear and extremely low friction. They are available commercially and Formula 1 teams apply them to their piston skirts. If you’re willing to pay for it, a DLC coating may solve any problems you have with piston wear.

The wear rate seems to be directly proportional to the force applied. The formula I found for wear is: wear volume = wear rate coefficient x normal load x sliding distance. So if you have a 10% increase in side wall loading due to an 88 mm crankshaft with an offset wrist pin you should have a 10% increase in cylinder wall wear and a 24% increase in piston wear if all else were equal. If a piston would last 300,000 miles in a stock engine before being worn out, it should last 240,000 miles in a stroker engine if all else were equal.

Personally, I would be happy reducing the service life of my engine to 240,000 miles if I got Ponyboy’s horsepower capability in return. A service life to 30,000 or 50,000 miles would be a steep price to pay. But with the right coating, the service life would hopefully not suffer at all.

naaman said:
So how many stroker engines are out there, and how many miles have the accumulated since the install? Any tear downs after a few thousand miles to asses whether wear and tear has increased?

+1

L_RAO · 15 July 2011

Honcho said:
The Super GT (former JGTC) NSX engine was a stock C32B modified for race duty and served from 2000-2003. Most of the internal components can be found on Toda's website, where they call the engine package "C35B". Output in race trim (100RON race fuel) is 500 hp. The grocery list:

C32B Block
C32B Heads with titanium valve springs and lightweight valves, bronze guides
ITB Intake with roof snorkel
84mm Stroker Forged Crankshaft
Lightweight forged pistons
High Lift Cams
Adjustable Cam Gears
Dry Sump Oil System
MoTeC engine management

Toda also sells the C35B as a crate engine for Japanese race teams.

First off...DROOL...

Second, it looks like Toda has 3 different camshaft offerings...has anyone ever installed a set?

sparky · 15 July 2011

L_RAO said:
First off...DROOL...

second that. WHAT a machine

:smile::biggrin:

Juice · 15 July 2011

The laundry list for that Toda crate seems nearly all to with the top side. You guys are comparing bottom end changes. I'm just saying there really isn't much valuable info there to go off of.

BATMANs · 15 July 2011

Ponyboy said:
Up and running again...after a very long time. 3.6L v2:

The biggest difference is a change to Wiseco pistons.......

When I did research for my GTO engine to be rebuilt with forged components to take on more power I decided that Wiseco was the way to go.

Just outta curiosity, what was ur thought process in selecting pistons? And which one did u get? 4032 or 2618 alloy?

I'm thinking about rebuilding the NSX engine to beef up the internals to take 15psi of SOS SC on pump gas and when i talked to Shad he said that he has had stellar success with the JE pistons. JE pistons seems to be a popular brand with many of the honda/acura guys looking at building some VERY fast cars for the drag.

Did u look into JE as well?

sparky · 15 July 2011

Honcho said:

Assuming that big bronze casting at the engine base is part of the engine solution and not just a stand ... what is it? Perhaps part of the dry sump system? or a very large engine mount ???

3.6L ScienceofSpeed Engine (NA Stroker)

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