NSX bhp/litre

[NoelWatson]

I've been having a debate about the NSX over on PH and was wondering about why the NSX had "only" 90bhp/litre when I recall Civics at the time had 100bhp/litre. Was it purely down to the 280ps voluntary agreement?

[simonprelude]

From memory it was more to do with the fact that Honda decided more than that from a V6 was classed as risky (rev limit etc), the 280ps was applied to most cars out there but a lot broke it anyway, just unofficially.

[NoelWatson]

From memory it was more to do with the fact that Honda decided more than that from a V6 was classed as risky (rev limit etc), the 280ps was applied to most cars out there but a lot broke it anyway, just unofficially.

My question partly came from Detlef dynoing his Type-R engine and getting 318ps. I assumed that the "standard" NSX adhered to the limit and Type-R were given more leeway.

[AR]

My NA1 R dynoed at 293 with H/E and my 93 3.0 at 296 with H/E, so is not far off the mark.

[markc]

I've been having a debate about the NSX over on PH and was wondering about why the NSX had "only" 90bhp/litre when I recall Civics at the time had 100bhp/litre. Was it purely down to the 280ps voluntary agreement?

It gets harder to achieve high bhp/litre with larger engine displacement. At the time 100hp/litre was extrodinary (for a car). To attain 90bhp/litre with the ECU computing capacity and fueling accuracy of the time (late 1980's) was quite an achievement.

Honda probably used a logical scaling of the 1600/1800cc Civic/Integra outputs while retaining safe margins, drivability and longevity.

The volunteery agreement might have had a little influence on the figure i.e. Honda held back a bit with the fuel/ignition map to ensure the engine didn't make more than 280ps.

It's certain that today an mechanically identical engine could make a lot more power by using more/better sensors (Airflow/Knock/O2 etc), more powerful ECU (CPU, memory etc), higher pressure fuel injectors etc.


My question partly came from Detlef dynoing his Type-R engine and getting 318ps. I assumed that the "standard" NSX adhered to the limit and Type-R were given more leeway.

No disrespect to Detlef but as we know unless it was back to back with another standard car/engine on the same facility on the same day etc that figure doesn't count for much in itself.


My NA1 R dynoed at 293 with H/E and my 93 3.0 at 296 with H/E, so is not far off the mark.

Same comments as above. Those figures look to be consistent with Kevin and Leigh's non R cars with similar H/E treatment.

We need to get Chris and Fusilov's cars down to TDI :)

Cheers

Mark

[NoelWatson]

It gets harder to achieve high bhp/litre with larger engine displacement. At the time 100hp/litre was extrodinary (for a car). To attain 90bhp/litre with the ECU computing capacity and fueling accuracy of the time (late 1980's) was quite an achievement.

Honda probably used a logical scaling of the 1600/1800cc Civic/Integra outputs while retaining safe margins, drivability and longevity.

The volunteery agreement might have had a little influence on the figure i.e. Honda held back a bit with the fuel/ignition map to ensure the engine didn't make more than 280ps.

It's certain that today an mechanically identical engine could make a lot more power by using more/better sensors (Airflow/Knock/O2 etc), more powerful ECU (CPU, memory etc), higher pressure fuel injectors etc.



No disrespect to Detlef but as we know unless it was back to back with another standard car/engine on the same facility on the same day etc that figure doesn't count for much in itself.



Same comments as above. Those figures look to be consistent with Kevin and Leigh's non R cars with similar H/E treatment.

We need to get Chris and Fusilov's cars down to TDI :)

Cheers

Mark




It gets harder to achieve high bhp/litre with larger engine displacement



I'm trying to work out why this would be (assuming you are allowed to increase no of cylinders). Why would losses be non-linear?




To attain 90bhp/litre with the ECU computing capacity and fueling accuracy of the time (late 1980's) was quite an achievement.


So why not diddle with ECU in 1997 facelift and take advantage of more advanced computing power - surely it wouldn't cost too much more seeing as they made mods to the engine anyway. The official output of both 3.0 and 3.2 was 280ps according to the book, so I can only think that the aggreement had a large influence.....

[simonprelude]

So why not diddle with ECU in 1997 facelift and take advantage of more advanced computing power - surely it wouldn't cost too much more seeing as they made mods to the engine anyway. The official output of both 3.0 and 3.2 was 280ps according to the book, so I can only think that the aggreement had a large influence.....

Because the emissions ruling etc get more strict with time, just look at the LEV ECU on the post 02 cars etc.

[markc]

I'm trying to work out why this would be (assuming you are allowed to increase no of cylinders). Why would losses be non-linear?

I believe it's primarily due to internal friction of the extra cylinders and valves. It is possible as many of the modern multi-cylinder, high performance engines from Audi, BMW, Porsche, Ferrari etc show.

The Macca F1 (6.1Ltr, V12) managed 100hp/litre back in 1992 only by using the then very latest engine management... cost quite a bit tho' ;)


So why not diddle with ECU in 1997 facelift and take advantage of more advanced computing power - surely it wouldn't cost too much more seeing as they made mods to the engine anyway. The official output of both 3.0 and 3.2 was 280ps according to the book, so I can only think that the aggreement had a large influence.....

Honda just fiddled with the existing ECU really, it's much the same as the 1995> one that added the requirements for OBDII compliance, which is little more a mild update of the original 1990 unit. They didn't fit a fundamentally differant, much more powerful ECU so couldn't up the ante on the ignition and fueling front... more's the pity :(

As Simon says emissions regulations have forced the manufactureres to make their engines cleaner, which though making them generally more efficient (a good thing), it does hold back their peak power potential.

Cheers

Mark

[NSXGB]

The Macca F1 (6.1Ltr, V12) managed 100hp/litre back in 1992 only by using the then very latest engine management... cost quite a bit tho' ;)




Was it not in 1991\1992 when the Maclaren F1 and the BMW E36 Evo were released which both had 100 bhp per litre. The first production cars to claim this accolade?

[simonprelude]

Was it not in 1991\1992 when the Maclaren F1 and the BMW E36 Evo were released which both had 100 bhp per litre. The first production cars to claim this accolade?

The Daihatsu Charade was the first 100bhp per litre road car ;)

The GTti was able to claim to be the first production car to produce 100bhp per litre and was also the fastest 1 litre production car made. It also had a fairly successful rally career competing in the RAC Lombard Rally in 1989 and 1990 and was highly competitive in the Safari Rally. The GTti won class honours many times and was able to mix it with some of the 2 litre cars on occasion troubling some of the 4wd cars !

http://en.wikipedia.org/wiki/Daihatsu_Charade

[markc]

Was it not in 1991\1992 when the Maclaren F1 and the BMW E36 Evo were released which both had 100 bhp per litre. The first production cars to claim this accolade?

I thought the M3 evo came along in 1995 with the update to the 3.2Ltr engine. Even the 1992 3Ltr car had 286bhp though.

Despite also using a Bosch MoTronic ECU (2 of them?) the Macca is in a differant league :D

Mark

[NoelWatson]

Was it not in 1991\1992 when the Maclaren F1 and the BMW E36 Evo were released which both had 100 bhp per litre. The first production cars to claim this accolade?

I think the Civic had 160ps from 1.6l back in 1989

http://asia.vtec.net/spfeature/vtecimpl/vtec1.html

"The pinacle of VTEC implementation is the DOHC VTEC engine. The first engine to benefit from VTEC is the legendary B16A, a 1595cc inline-4 16Valve DOHC engine with VTEC producing 160ps and first appearing in 1989 in the JDM Honda Integra XSi and RSi."

[AR]

Are we leaving wankels out???

[Ewan]

I don't think we can compare rotary engines on the same basis - in racing, their capacity is doubled for classification purposes, and in Japan the tax rating is 1.5x their capacity.

That said, the Mazda 787B car that won Le Mans in 1991 (still, IMHO, the best sounding racing car ever produced - sounds like it's trying to tear itself apart ... check out
http://www.youtube.com/watch?v=K1BWv7iPFUg
http://www.youtube.com/watch?v=9675TKafw3g
That has to be the angriest sounding idle in the world...), produced around 700bhp on a 2.6L rotary, so for comparison purposes would work out at about 135bhp/L. That is pretty impressive. If you listen to the thing, it's got no crank inertia to worry about - anything that can pick up and drop revs that quickly is going to be hard to beat.

The Mazda Furai is a 3-rotor engine (http://www.youtube.com/watch?v=oEOHn7rspsk&feature=related), presumably in the region of 1.9L and developing 444bhp, so with the doubling of capacity that would come in at more like 117bhp/L.

When the S2000 came out, it had the record for the highest specific output of any production NA engine - in Japan, 120bhp/L. Even a 360 Challenge Stradale tips out about 118bhp/L, and I can't think of any NA car with more than 120...?

Look at 6cyl performance NA cars today
- the Evora; ~80bhp/L.
- Cayman S; ~90bhp/L
- Carrera S; 100bhp/L

Maybe the old NSX wasn't too shabby after all :)
Even

[AR]

I don't think we can compare rotary engines on the same basis - in racing, their capacity is doubled for classification purposes, and in Japan the tax rating is 1.5x their capacity.

That said, the Mazda 787B car that won Le Mans in 1991 (still, IMHO, the best sounding racing car ever produced - sounds like it's trying to tear itself apart ... check out
http://www.youtube.com/watch?v=K1BWv7iPFUg
http://www.youtube.com/watch?v=9675TKafw3g
That has to be the angriest sounding idle in the world...), produced around 700bhp on a 2.6L rotary, so for comparison purposes would work out at about 135bhp/L. That is pretty impressive. If you listen to the thing, it's got no crank inertia to worry about - anything that can pick up and drop revs that quickly is going to be hard to beat.

The Mazda Furai is a 3-rotor engine (http://www.youtube.com/watch?v=oEOHn7rspsk&feature=related), presumably in the region of 1.9L and developing 444bhp, so with the doubling of capacity that would come in at more like 117bhp/L.

When the S2000 came out, it had the record for the highest specific output of any production NA engine - in Japan, 120bhp/L. Even a 360 Challenge Stradale tips out about 118bhp/L, and I can't think of any NA car with more than 120...?

Look at 6cyl performance NA cars today
- the Evora; ~80bhp/L.
- Cayman S; ~90bhp/L
- Carrera S; 100bhp/L

Maybe the old NSX wasn't too shabby after all :)
Even


They also get multiply for road tax overhere. :)

[NSXGB]

I thought the M3 evo came along in 1995 with the update to the 3.2Ltr engine. Even the 1992 3Ltr car had 286bhp though.

Despite also using a Bosch MoTronic ECU (2 of them?) the Macca is in a differant league :D

Mark

Yup, you are right it was 1995 the Evo came along. I just remembered a poster I saw at a BMW dealership boasting about the 100bhp per litre with obviously both cars having a BMW engine. I looked up the date of the F1 release being 1992...
I remember the Charade GTti but being a FI, that's cheating, right? :)


Are we leaving wankels out???

Always someone got to lower the tone... :)

[JQD84983]

Definately 100bhp/litre for a NA engine was a real achievement.

For me the engine is NSX is easily capable of achieving 320bhp or more if Honda spent the time developing it and adding special components etc. For me they had the voluntary limit that held them back and they reasoned that the weight gains for the NSX were more important and spent development money there.

[markc]

The Daihatsu Charade was the first 100bhp per litre road car ;)

A mate of mine had one of them back in the day. Sounded fantastic as most triples do :)

FI is definitely cheating tho'


Are we leaving wankels out???

Not really comparable and neither are 2 strokes.

I remember the first big'ish 4 stroke production engine to really lift the hp/ltr ratio was the 1984 Kawazaki GPZ900R which managed 115hp from 908cc i.e. 126hp/ltr. It set the blueprint for the modern superbike. (Tom Cruise rode one in Top Gun :) )

Another mate of mine had one of the first GPZ900R's in the country and was treated like a rock star when he took it to the Isle of Man for the 1984 TT. Near standard GPZ's finished 1st and 2nd in the equivalent of the Superstock (Production 1000cc) class that year :D

The latest superbikes make 180hp/ltr!

Mark

[NoelWatson]

I believe it's primarily due to internal friction of the extra cylinders and valves. It is possible as many of the modern multi-cylinder, high performance engines from Audi, BMW, Porsche, Ferrari etc show.



But surely this is a linear relationship. Why should a 3 litre straight six be less than twice as powerful as a 1.5 litre triple. Crankshaft needs to be longer and therefore a lot stiffer maybe.

I don't buy the argument that the changes due to emissions made a massive difference. On a Peugeot 205/309, the 1.9 dropped from 130 to 118 bhp due to switch to unleaded and reduced compression ratio, but I am not aware of anything as dramatic happening with the NSX as it was designed to use unleaded from the outset.

[markc]

But surely this is a linear relationship. Why should a 3 litre straight six be less than twice as powerful as a 1.5 litre triple. Crankshaft needs to be longer and therefore a lot stiffer maybe.

Good question and I don't the answer. The number of components and consequently internal friction simply increases linearly in that example. Assuming the extra cylinders get equally efficient inlet and exhaust systems, not easy with a much longer engine, perhaps the power would as well?

Doubling the output of 2 triples using a V6 arrangement is a differant prospect as there is a more complex valve gear to drive so the internal friction is higher. Maybe this is why the NSX engine doesn't match the Civic/Integra for bhp/ltr?

There's some good information on the intricies of all combinations here... http://www.autozine.org/technical_school/engine/smooth1.htm

Cheers

Mark

[Ferris Bueller]

But surely this is a linear relationship.

-ish.....assuming identically sized cylinders. BMEP (the proper way of comparing different engines) would be theoretically similar but physics presents the biggest challenges i.e. actually getting the air in, as higher vol effs are difficult to come by, and piston speed i.e. stroke in effect - limited by materials etc at around 20 m/s.

ETA (Wikipedia not the best source but the easiest to reference):-
http://en.wikipedia.org/wiki/BMEP (http://en.wikipedia.org/wiki/BMEP)
http://en.wikipedia.org/wiki/Volumetric_efficiency
http://en.wikipedia.org/wiki/Mean_piston_speed

[NoelWatson]

-ish.....assuming identically sized cylinders. BMEP (the proper way of comparing different engines) would be theoretically similar but physics presents the biggest challenges i.e. actually getting the air in, as higher vol effs are difficult to come by, and piston speed i.e. stroke in effect - limited by materials etc at around 20 m/s.

ETA (Wikipedia not the best source but the easiest to reference):-
http://en.wikipedia.org/wiki/BMEP (http://en.wikipedia.org/wiki/BMEP)
http://en.wikipedia.org/wiki/Volumetric_efficiency
http://en.wikipedia.org/wiki/Mean_piston_speed


We were discussing BMEP over on PH, and the chap was saying that the NSXs has a pretty low munber, but I'm sure this is partly due to the short stroke design.

[Ferris Bueller]

We were discussing BMEP over on PH, and the chap was saying that the NSXs has a pretty low munber, but I'm sure this is partly due to the short stroke design.

Which brings you full circle as BMEP is a function of the power output and engine capacity.

You need short stroke for high revs i.e. piston speed is a limiting factor and good vol eff/gas flow to keep the torque up at high revs to get the power.

[NoelWatson]

Which brings you full circle as BMEP is a function of the power output and engine capacity.

You need short stroke for high revs i.e. piston speed is a limiting factor and good vol eff/gas flow to keep the torque up at high revs to get the power.


Not convinced this is still strictly the case - see Audi RS4 - 93mm stroke

[Ferris Bueller]

Not convinced this is still strictly the case - see Audi RS4 - 93mm stroke

Sorry, Noel, what are you getting at? Relatively longer stroke in the RS4 vs NSX so not the reason why it's got a higher specific output?

[NoelWatson]

Sorry, Noel, what are you getting at? Relatively longer stroke in the RS4 vs NSX so not the reason why it's got a higher specific output?

Your comment that you need short stroke to get high revs - Audi have managed to get the high revs with relatively long stroke - guess due to materials and variable cams/breating.

[Ferris Bueller]

Your comment that you need short stroke to get high revs - Audi have managed to get the high revs with relatively long stroke - guess due to materials and variable cams/breating

It is a limiting factor and the two are linked. Take it to an extreme, what stroke does an F1 engine have?

The RS4's engine is a very impressive bit of kit. In terms of stroke the
E46 M3 engine is similar and is a few hundred rpm behind, E92 V8 is a fair bit shorter than the E46 and revs higher. S2000 is inbetween at about 85. The longer stroke 2.2 US derivative has a red line 800 rpm lower - for a similar piston speed.

[Ewan]

Just to warm this topic up again...

See Ferrari have announced the replacement for the F430? It's not the 450 as Autocar was calling it, but 458 Italia...

4.5L v8, 9000rpm, 570 bhp = 126.6 bhp/L. Wow :)

http://cars.uk.msn.com/News/car_news_article.aspx?cp-documentid=148815472

[gumball]

Just to warm this topic up again...

See Ferrari have announced the replacement for the F430? It's not the 450 as Autocar was calling it, but 458 Italia...

4.5L v8, 9000rpm, 570 bhp = 126.6 bhp/L. Wow :)

http://cars.uk.msn.com/News/car_news_article.aspx?cp-documentid=148815472

Lovely isn't it, this is what I was hoping for from Honda.

[TheSebringOne]

Side profile looks like the 360 which I prefer to the 430. Triple zorst just like the F40! I wander if their F1 know how has anything to do getting that much bhp per litre!

[TheSebringOne]

Found this on PH!

http://www.pistonheads.com/ferrari/default.asp?storyId=20348

[gumball]

I'm not one these "I hate flappy paddles" people, but I think the sound has lost some rythm with the changes being so quick.
Yes that sounds odd to me too, but maybe some will know what I mean. :)

[simonprelude]

The new Ferrari looks like they bought the rights to the HSC.