dakkrin

04 ZX-10R 9.92 @ 147.4 mph 161.8 hp
05 R1 9.92 @ 149.3 mph 159.8 hp

thanks i couldnt remember where i read that from just knew it was true
less hp, same 1/4 time, higher trap speed

'04 ZX-10R 9.92 @ 147.4 mph 161.8 hp
'05 ZX-10R 9.78 @ 148.5 mph 158.4 hp
another good example i didnt notice before, even lower hp, but even better 1/4 mile time, and trap speed is good also compared to the highest hp one

78novacaine

iTrader: (2)

i know this isnt the case for "every single supra" but most of the supras you see making these HUGE numbers, are only making them for a couple hundrd RPM. which would you rather have, a 408 twin turbo, making say, 700 ft lbs @ 3500 rpm, and 900 rwhp @ 6k rpm, or a supra making 1200 hp and 7-- ft lbs, but only from 6200-7k rpm. i would much rather have that power under the curve.

but back to the original topic, i am curious as to why ford has not tried to go bigger with either the SOHC or DOHC mod motor, i mean, if they are so far superior to an OHV motor, why dont they just make say, a 400+ C.I. version to destroy the ls7? there has to be something holding them back technology wise from being able to up the C.i. that much, that or the overall size and weight of a 400+ c.i. ohc motor would just be insane

engineermike

Looks like you can twist the data however you want it to look. My point was that the two are too close to distinguish with statistical deviation. I guess I could twist the numbers in my favor too. . .

'05 ZX-10R 9.78 @ 148.5 mph 158.4 hp
'05 R1 9.92 @ 149.3 mph 159.8 hp

10R has 1.4 less hp and runs .14 seconds quicker despite this. Sheesh. . .

On top of all that, keep in mind that the '04 and '05 10R are identical, and the '04 and '05 R1 are identical, further showing that the differences there are totally statistical. You can't claim one has more power and the other a better curve so the better curve is faster. In fact, the 10R has a much more desireable curve, making 7.5% more peak torque and as much as 28% more torque at 7000 rpm:

http://www.sportrider.com/features/1...en_bikes_dyno/

Mike

dakkrin

.15 sec is very significant for me, when at the track thats a loss, especially if the competitor has equal hp, why is one .15 sec faster, they have the same hp/l

and street racing, losing by almost .2 sec would suck if you had the same or a little more hp

obviously another factor is in play and i'm glad they didnt just increase hp to make the vehicle faster thats all the point was

engineermike

Well. . . I make 700 rwhp, and it comes between 5300 and 6200 rpm. My motor never goes outside that range at the track or on the dyno. If the car has a proper converter, then the rpm range looks really narrow on the dyno but isn't. But this is all really beside the point, as the original poster said that a given turbo will make more power on a large v-8 than it will on a 2JZ, which simply isn't true.

There's alot more to engine design than "let's just make a 400 ci mod motor to destroy the LS7". I'm just guessing here, but I bet it was cheaper and easier to meet emissions requirements by adding a supercharger to get 550 hp out of a 5.4, rather than trying to re-design the bottom-end to add 100 cid.

Mike

78novacaine

iTrader: (2)

were those all done by the same rider on the same day at the same track? because otherwise such miniscule differences really prove nothing, the lower horsepower bike could have had a better rider, cooler day, better track prep, etc, etc. also is there a weight difference between the bikes/riders? that could also account for the different times

engineermike

Have you ever ridden a stock SS 1000 down the dragstrip? These bikes will wheelie at 90 mph in full tuck using no clutch. A tenth or two is simply differences in rider. The average Joe can't do better than 10.4 - 10.6 on these bikes stock. Lower it and change the sprocket and they are running 9.3. The difference between 9.7 and 9.9 in a magazine test is nothing. And besides, I was pointing out that the 10R was faster than the R1 by .15 even though it had lower power, not the other way around.

78novacaine

iTrader: (2)

i know there is a lot more to engine design than that, that is why i was asking what it is that is limiting cubic inches in ohc motors, because there is obviously some mechanical factor preventing them from easily reaching higher cubes. like maybe maximum bore/stroke without a much larger/heavier block?

engineermike

No kidding. That's been my point all along. dakkrin claims that the R1 is faster because it had a better power curve, and neither statements are true. A quick look at the numbers shows that the difference in hp and quarter mile is statistically insignificant, but the dyno charts show the 10R has a better curve.

engineermike

Funny you point that out. I did some more looking and, consistently, the bikes with more power run better at the track. Again, with stock sportbikes, you can't really look at et since they are so dependent on the rider's ability to deal with wheelieing. But, the mph is definitely higher with the higher hp bikes. Oddly enough, the 1000 class bikes have the same hp (for more hp/liter), but are significantly lighter than their open-class 1200 - 1400 cc brethren, and as a result are quicker and faster in the quarter mile.

engineermike

Ford sticks with the little 3.55" bore in the mod motors. They did produce a crate engine with a 3.7" bore but no one seems to go beyond that, probably due to the 3.937" bore spacing. That small bore spacing makes the mod motor 1.5" shorter axially than an LSx.

mzoomora

iTrader: (36)

All this talk about HP and nobody is talking about torque.
Who cares if an engine can make 100 hp/l if it cant make a desirable torque curve for it to be drivable. The OE's RARELY design a race car for public sale (Z06 and the like being exceptions), so torque is every bit as important as HP. And take into account that the Z06 is a track car not a drag car, so power out of a turn (broad torque curve) is very useful. Take two N/A engine making the same HP and one is smaller, it most likely is turning more RPM (not always the case, but usually).

HP/L is truly ricer math and is a useless formula unless you are displacement limited. High output small displacement engines that are N/A usually dont do well with MPG either.

Also, do not bring up the 3.4 Vs 3.8 again. The 3.8 was a broad range engine used in many cars, but when in the same chassis using the same transmission performed nearly identical to a 3.4 and was a better city driver. The 3.4 needed a manual trans to really work well, the 3.8 didnt because of a better power band. Sure the 3.8 was not a performance engine, but in its one-size-fits-all configuration performed every bit as well as the 3.4 in the same circumstances.

78novacaine

iTrader: (2)

ok, i was just wondering. because i think if they redesigned the block to take a larger bore, they could easily be selling lets say 5.7 L DOHC gt's putting out around 400 hp or so. i have a lot of respect for the DOHC design, but like has been said many times before, there is a huge tradeoff with overall size and weight, and like you said just now, if they were to increase the bore spacing, it would make a big and heavy motor even bigger and heavier. the question is, will the added power be enough to offset the weight difference?

germeezy1

Look at the size of the 5.4 DOHC and how much it makes the GT500 weigh.

black_knight

iTrader: (1)

It is physically larger. When they stuck it in the cobra R they needed the bubble hood to fit it in there. I don't know how much heavier it is in aluminum form but it's certainly larger. And obviously it still didn't have enough power N/A to compete with the LS2 (much less the ls7), so they had to take an already heavy motor and add a supercharger (heavy) and make it iron (heavy).

Louie83

iTrader: (3)

Since we have devoted almost 28 pages to talking about HP/L, I think it's about time we start talking about HP/Camshaft.

FieroZ34

iTrader: (1)

Ok, Fiero chassis with a 5-speed. A stock DOHC will trap 4 tenths faster than a 3800 S/C, as well as having a faster 60', and a higher trap speed.

B T

>>>

I'd maybe even settle for HP/L "ifter".

engineermike

All this talk about how big the mod motors are got me thinking. . . just how big is the mod motor as compared to the LSx? I did some digging and found the following. . .

LS1
height: 27.5"
width: 24.75"
length: 27.5"

5.4 DOHC (car intake)
height: 28.5"
width: 28.25"
length: 23.625"

So, the 5.4 DOHC is 1" taller, 4" shorter length, and 3.5" wider (that's 1.75" per side) than the LSx. This comes from an engine that has a 0.170" longer stroke and 0.600" longer rod than the beloved LS7, so I suspect some of the width comes from a tall-deck block required to fit the rod and stroke, not just the OHC valvetrain. In fact, the 5.4 block deck height is a full 0.830" taller than the LSx, so you can't say the motor is so wide just because of the DOHC. I expected the mod motor to be shorter length because of the smaller bore spacing and bore, but 4" seems like alot. 2" seems more reasonable, but the sources say 4". Just thought someone should put some numbers to these claims and, frankly, I'm a little surprised at the results.

Saying that the 5.4 DOHC SC in the GT is what makes it heavy is kinda' silly. I mean, hey, the F-body has the ultra-light LSx in it, and it weighs even more than the Ford GT. Could it be that Chevy went through alot of effort to make the ZO6 a light car? But, yes I'm sure the iron-block, supercharged, DOHC 5.4 is heavier than the aluminum-block, Titanium rod, 7.0. We won't bring up hop-up potential, though, since the iron-block and supercharger give the GT motor a huge advantage there. . .

Mike

B T

>>>

Just "nit picking" here , why are you always bringing up a Forced Induction application vs a Normally Aspirated one?


Thanks.