SoCal EJ1

I've read in a few threads of people saying that a built/turbo'd SOHC will put out better torque numbers than DOHCs with the same/similar specs. First off, is this true? and if so, why? I searched both current and archived threads and didn't find anything relevant.

PINKS

Uncomparable

SoCal EJ1

I don't see why it wouldn't be. It's not simply a preference issue, they both produce numbers so therefore they can be comparable.

thomas@LPS

the majority of the sohc honda engines are long stroke small bore engines. were as most of the dohc are short stroke large bore engines. do a little internet searching im sure you can find tons of write ups about this topic.

boosted92

A SOHC is usually going to be turning less revs and be less efficient than a DOHC motor.

That means more reliance on the turbo to make the power, and more boost pressure. More boost pressure means more torque at lower RPM's, and more overall torque for any given peak horsepower level. Look at some of the D-series on here, some of them are taking 30psi to make 450 WHP on a T3/TO4E 57-trim, that's 10psi more than a DOHC motor. So you're going to be seeing more mid range torque. I don't think it would be out of this world to suggest a SOHC will make more torque than a DOHC.

THEDirtyDseriesWOOT

at certain power levels the sohc makes more tq.. but dohc is always gonna make more power d-series heads dont flow for ****..

WickedHonda00

Let's not forget that HP is a result of TQ and RPM. It's not that a D series will make more torque than ALL B series setups, only some of the mild setups. The D series have 92mm strokes I believe, and typically, most B series have between 77mm-89mm, unless custom crank assemblies are used.

However, more peak torque doesn't equate to a faster car, nor does it mean there is more gratification in driving the car. (I assume this is where the OP is going with this.)

A B series setup with a 4000RPM peak tq plateau of 190wtq could very well be faster than a D series with a 2500RPM peak tq plateau of 220wtq. Couple that with shorter gear ratios and higher RPM's and anyone could agree the B series is a much better platform. Just some food for thought.

In addition...try not to drag the B series platform in the mud of the D series.

HiProfile

Look at the specs yourself: http://www.raceseek.com/honda_specs.htm

D16's have a longer stroke than B20's. Longer stroke means better low-mid range, but they won't want to rev as high - mechanically or HP-wise. The reason B16's make so much high-end & rev so well is the same reason they're gutless out of boost/rpm - They have half of an inch shorter stroke than a D16.

Usually a 220whp D16 is making the same peak torque as a 300whp B-series. Adding a cheap cam & IM helps D16's flow much better up top.

THEDirtyDseriesWOOT

u can rev a d to 9k easy u just dont make power that high lol

WickedHonda00

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HiProfile &raquo;</TD></TR><TR><TD CLASS="quote">Look at the specs yourself: http://www.raceseek.com/honda_specs.htm

D16's have a longer stroke than B20's. Longer stroke means better low-mid range, but they won't want to rev as high - mechanically or HP-wise. The reason B16's make so much high-end & rev so well is the same reason they're gutless out of boost/rpm - They have half of an inch shorter stroke than a D16.

Usually a 220whp D16 is making the same peak torque as a 300whp B-series. Adding a cheap cam & IM helps D16's flow much better up top.</TD></TR></TABLE>

Which is supporting my point that more tq doesn't equate to a faster car at all. RPM and gearing have just as large a factor as peak tq. There is also alot less sidewall force on the smaller stroke motors,such as the B16, allowing it to rev to 8-9k much more reliably.

Also you have to consider the fact that B series are able to use larger turbo's while still having a decent powerband due to the RPM and higher flow rates of the head. At least in stock form...

THEDirtyDseriesWOOT

tq does have alot to do with how fast u go in a straight line.. my car made 40 more ftlbs than my buddys and he made 60 more hp and had about 800more rpms of powerband .. cars weigh about the same my car eats his all day long.. from a dig or a roll .. tq is what wins races..

S@nt0s

plain and simple
300whp B series and a 300whp D series the D series will yeild more torque

thats just like a 300whp LS-T will make more torque then a 300whp Vtec Bseries


what is it you want out of your set up is what you need to be asking yourself.

quicksilver1689

exatly you nailed that one.

93supercoupe

remeber, to get 300 on a less efeicient motor is going to take more boost pressure.

More boost pressure is going to make more torque, so its not all depending on bore and stroke size.

lets say a 300HP ls takes 20PSI ona 57trim, and the LSvtec takes 17PSI, the LS will have more torque from the added boost, and not becuase LS's have "more torque"

Turn the boost up on the LSv, and u will have equal torque and more HP.

S@nt0s

^.... true adn false..

perfect example that i have seen time and time again...

i made 250whp 226ft lbs on a completely bone stock LS with a 57 trim t3t4 on 10psi.....

the aveage GSR/LsVtec on 10psi stock will range from 190-210ft lbs. yet yield more HP 260-310...


and the avg. stock D series on 10psi depening on turbo ranges from 180-220whp with torque not far behind...



Modified by S@nt0s at 9:33 AM 4/18/2007

93supercoupe

u have to take into consideration the better flowing head, and the stroke differences between the motors.

93supercoupe

why would a LS make more torque than an LSv if all other things being equal?

Im really asking b/c i always see people say this, and even have actual numbers to prove, but i dont know why.

Vtec heads flow better and have 2 cam profiles, and thats 2 HUGE steps better than LS's.

THEDirtyDseriesWOOT

the better you head flows the higher the hp.. witha smaller amount of tq.. at 10psi your making 200tq.. on a vtec head its gonna stay 200tq but hold the tq longer in the rpms thus making a higher amount of hp.. wixh really means nothing tq is what wins the race.

WickedHonda00

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93supercoupe &raquo;</TD></TR><TR><TD CLASS="quote">why would a LS make more torque than an LSv if all other things being equal?

Im really asking b/c i always see people say this, and even have actual numbers to prove, but i dont know why.

Vtec heads flow better and have 2 cam profiles, and thats 2 HUGE steps better than LS's.</TD></TR></TABLE>

The guy above us answered that already...and I think he could be right about the boost pressure effecting the tq output. I've seen those Cobalt SS/SC's stop making HP after about 18psi on their small Eaton superchargers, but the tq jumps dramatically per every lb added to the intake. Kinda of strange, but at some point the charger or turbo will stop benefitting the top end and start increasing low and mid range tq, thus not really effecting the peak HP. This helps explain the closely related #'s tha LS motors put out. They sometimes have as much Tq as HP...if the turbo is small enough.

From what I understand is this:

250hp @10psi &lt; 250hp@15psi when measuring the TQ ouput at any given RPM. Apparently the high boost factor has some effect on the tq output of the motor--&gt; probably because it's approching the efficiency range of the compressor map as the boost pressure rises, therefore the air displacement is greater than the same turbo boosting at a lower pressure. (This is what I gather from the thread)

Hp has no place in this conversation, since it is merely a factor of Tq and RPM, and since RPM has such a huge effect on the peak HP, it's hard to compare an LS setup to that of a GSR, B16, or Type-R setup.

trini-gsr

i'm still not getting how a d-series produces more tq than a b-series when it has less displacement. i can see maybe, if both motors are making 300whp, the d-series might have more tq, but it'll be running more psi or the turbos might be different, etc...so that's not really a fair comparison...

i think a better question is...if you run the SAME turbo at the SAME psi on a d-series and a b-series motor...which one produces more tq?

SoCal EJ1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by trini-gsr &raquo;</TD></TR><TR><TD CLASS="quote">i'm still not getting how a d-series produces more tq than a b-series when it has less displacement. i can see maybe, if both motors are making 300whp, the d-series might have more tq, but it'll be running more psi or the turbos might be different, etc...so that's not really a fair comparison...

i think a better question is...if you run the SAME turbo at the SAME psi on a d-series and a b-series motor...which one produces more tq? </TD></TR></TABLE>I believe once upon a time a 1.6 liter b-series existed...

WickedHonda00

Well, that's not too fair of a comparison either, that is, comparing the D and B using the same psi. The D series has a longer stroke, a much longer stoke that the B16, and I think 5mm longer stroke that the GSR, and 3mm longer than the LS and B20 stoke. Bore width only plays a small part in peak tq, at least not as much of a role as stroke. Same applies to intake manifolds...the longer the runner, the more torque is made, and visa versa w/ short intake runners. Somehow length, or "leverage" has a key role in tq.

Regardless, this is a good conversation since it brings up why I believe in maxing out a smaller turbo rather than using the larger ones..

A disco potato pushing 15psi to squeeze out just over 300whp tends to make a bit more tq than a larger turbo such as the 60-1 pushing 8psi to make the same peak power. Plus the smaller turbo will have a much broader powerband, due to the smaller compressor range. Personally, I think you should set your goal, and use the smallest turbo possible to make that goal happen...even if it takes 20psi of boost, you'll manage to have a larger powerband w/ loads more tq. That's what I think.

HiProfile

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by WickedHonda00 &raquo;</TD></TR><TR><TD CLASS="quote">
Which is supporting my point that more tq doesn't equate to a faster car at all. RPM and gearing have just as large a factor as peak tq. There is also alot less sidewall force on the smaller stroke motors,such as the B16, allowing it to rev to 8-9k much more reliably.

Also you have to consider the fact that B series are able to use larger turbo's while still having a decent powerband due to the RPM and higher flow rates of the head. At least in stock form...</TD></TR></TABLE>

Now consider this: given the same flowbench, the sohc vtec head will flow ~170cfm while a b16 head will flow ~230cfm. Thats a HUGE difference if you're trying to make 400whp+. It means torque will drop due to the head not supplying air. Stroke is really a small part in the big picture. I've seen HUGE discussions about over-square motors, under-square, etc, which relates to bore vs stroke, and there's not really a silver bullet that dictates engine dynamics based on just TWO measurements.

Also if you look at the transmissions, you can tell what the motors were designed for. B16's have rediculously short gears, while the D16Z6 trans is about the same as the LS.

WickedHonda00