American BHP measurement

[Paul_S13]

Do they measure it differently in the U.S.?

I ask because on another forum there is someone asking for a BHP estimate, his spec is as follows...

ca18det
blacktop SR turbo( larger t-25 than stock ca)
440cc injectors/ walbro fuel pump
blitz LM front mount
blitz DD bov
blitz NUR spec exaust
Z32 maf
apexi super afc
Blitz sbd II/ powermeter running aprx 12psi
blitz downpipe w/ Bee*R test pipe

Alot of other members of that board are saying he will have 300bhp @ the crank!! I personally think he's not going to get anywhere near that at such a low boost on a small turbo, also there petrol is something like 93RON, this also won't help if your chasing large bhp.




:confused: :confused: :confused:

[Martin T]

The answer is yes Americans do measure BHP slightly differently, but an American BHP is more then a British BHP. (about 0.99 american BHP to 1 British BHP.
PS is german for Horsepower (the word it comes form translates directly to Horsepower) There is about 0.98 British BHP to one PS.
His figures look very optimistic without cams etc and I would say that he's looking at more like 240 BHP@flywheel, less with 95RON (probably lose about 10 BHP to avoit pinking.)

[Paul_S13]

Originally posted by Martin T
There is about 0.98 British BHP to one PS.
His figures look very optimistic without cams etc and I would say that he's looking at more like 240 BHP@flywheel, less with 95RON (probably lose about 10 BHP to avoit pinking.)

Thats the sort of power I would expect, there is also another post that claims there is someone with a standard T25 @ 15psi with 225bhp @ the wheels!

[Martin T]

Cold day?

[Paul_S13]

Originally posted by Martin T
Cold day?

More like a cold front of bull****! :D

[Papa Lazarou]

Loads of bull**it artists about I think. Once read someone claiming 300 rwhp from an SR20 red top with according to him stock turbo, FMIC, FPR, fuel pump, SAFC and boost controller @ 15 psi. Or close to this anyway. No-one else believed him either... Guy didn't have a clue what he was on about.

[Papa Lazarou]

PS the S14 is a blacktop (or one of the black tops rather) perhaps he had a T28?

[Paul_S13]

Originally posted by Papa Lazarou
PS the S14 is a blacktop (or one of the black tops rather) perhaps he had a T28?

I replied that the blacktop SR's had a T28 and even with those mods your not going to see 300bhp at 12psi!

[andyf]

It's been debating on aussie BB's, that the main reason for American's quoting things as having unreasonably large power is down to the dyno's. American's seem to run predominately one top, whereas the UK/Ausland use more 'reliable' dynometers and get more realistic results.

[Kes]

I think there are a couple of factors in this one.

The US HP measurement is not strictly different, the difference is in the correction factors applied. When a dyno run is done, the air pressure and temperature are measured, then a correction factor applied to a standard set of conditions. As an example of this, have a look at Papa's dyno sheet in the tech section, there is one figure quoted for meaured BHP, and one for corrected. In Europe we use the DIN system for corrections, in the US they use the SAE, which seems to give higher figures when the factors are applied.

I also get the feeling that the US guys quote 'rwhp' ie measured on a dyno, but the figures they quote have a transmission loss measurement / percentage already applied in there. There 'rwhp' seems to be close to our flywheel BHP.

The other thing is, most of the guys I know in the US say never believe US dyno figures, since everything has to be bigger and better over there, so do the numbers...

They do have some nice cars over there, would be interesting to see them on a UK RR.

[Johnny]

I would have thought that American horses were bigger than the European horses ........ so for every 3euroBHP you get 1USBHP ... guess I was wrong :(

I mean, hell .. there cows are bigger as are there mellons (fruit)

[Robbie]

So what's the difference between a red top and a black top? (and a coat of paint isn't the correct answer!) I'm presuming the red top has stronger internals but what exactly?

[SteveCarter200]

Originally posted by Robbie
So what's the difference between a red top and a black top? (and a coat of paint isn't the correct answer!) I'm presuming the red top has stronger internals but what exactly?

AFAIK the main difference is that the black top (S14) has VVC whereas the redtop doesnt, although saying that the late 180SX' had the blacktop but without VVC.

IIRC....

S13 180SX 89>92 CA18DET with T25 turbo
S13 180SX 92>96 redtop SR20DET (no VVC) with T25H turbo
S13 180SX 96>98 blacktop SR20DET (no VVC) with T25H turbo
S14 Silvia/200SX 98> blacktop SR20DET (with VVC) with T28 turbo

[Papa Lazarou]

Originally posted by Kes
I also get the feeling that the US guys quote 'rwhp' ie measured on a dyno, but the figures they quote have a transmission loss measurement / percentage already applied in there. There 'rwhp' seems to be close to our flywheel BHP.


Makes a mockery of the "at the wheels" figure if they are including transmision losses though.

Definately something like this happening though. I have seen a US dyno printout posted showing 409 hp at the wheels from an SR engine. The car was running 550cc injectors, no NOS or anything and stated they were only running a 92% duty cycle. On a UK dyno 400 "wheel power" will work out in the high 400's "engine power". Correct me if I'm wrong but 550's are not going to support nearly 500 hp engine power, at least not without being completely and utterly maxed out.

[andyf]

This month's EVO has a very nicely put paragraph about DIN and SAE.

The American's chose the SAE method to measure horsepower, where you take an engine, put a straight through exhaust on, and run the thing.

The Europeans' (and others) chose DIN, where you take an engine, strap everything on to it, all the ancilliares, then run it. Because of the power sapped by bits and pieces, you have a lower figure than SAE.

[Kes]

I read some story about Ford having to re-quote their power figures for the mustang at some point, as the original was grossly inflated... Also, Aston Martin and Rolls Royce from about the 60s or 70s onwards wouldn't quote power figures for their cars, as they felt US companies were exagerating theirs, and it was better to say nothing and let people guess - they always guessed high!

[Goblinslayer]

I've been on snowmobiles in the US that are quoted in the brochure as being nearly 200 horsepower.
No way in hell was it the same power as my car....
Although bloody bloody fast... doing 100mph on a frozen lake on one is the scariest thing I've ever done :-)
On the other hand any vehicle where the advice for going through lumpy ground is "accelerate straight at the bumps and jump over them, cos if you try and go around you'll tip over sideways" is ok by me :D :eek:

[AshT_200]

Originally posted by andyf
This month's EVO has a very nicely put paragraph about DIN and SAE.

The American's chose the SAE method to measure horsepower, where you take an engine, put a straight through exhaust on, and run the thing.

The Europeans' (and others) chose DIN, where you take an engine, strap everything on to it, all the ancilliares, then run it. Because of the power sapped by bits and pieces, you have a lower figure than SAE.

Yeah, I heard something about this to, and I was told that the SAE method also removed all ansillaries, including alternator, waterpump (was externally pumped) so there would be no power losses.

[Martin T]

So if you take for example an Amercian made 900 RWHP Supra and convert it to British HP, you'll end up woth about 650 RWHP. (since they use SAE and also when they say RWHP, they really mean HP@ fly and are pointing that the car is rear wheel drive)