roller rocker cams

[manzano]

Pche,

Only the 'S' cam will be available shortly, as far as I know.
JWT didn't quote any numbers, as they were still in R&D. But I would expect a minimum of 8-10 rear-wheel HP. Also, the roller rockers may enable JW to make the cam ramps more aggressive without putting strain on the valvetrain.

One of the compact car mags did a comparo with various JWT grinds, hopefully another member can recall the exact issue.

Generally speaking, here's what you can expect from two cams with similar durations

1) The cam with less aggressive ramps (to allow for the use of stock springs and retainers) will have less torque and less peak HP.

2) The cam with more aggressive ramps (translated: valves open fast) and more total lift (sometimes with a few degrees LESS duration) will make more torque throughout the majority of the RPM range.

hope this helps

[G-Forces]

Originally posted by manzano
But I would expect a minimum of 8-10 rear-wheel HP.

That is VERY, VERY impressive! Impossibly impressive I'd have to say.

[manzano]

Average dyno gains on their pre-00 SR20 cams is 8 rw hp with no other mods, and they can squeeze another few ponies if they can take advantage of the roller rockers to add some more lift while keeping their 260 duration.

And don't be surprised if that's what JWT pulls off. Maybe there is a Santa Claus...

[manzano]

OR

you can have the same lift and duration, and build more aggressive ramps, so the valve sits longer on the 'nose' of the cam. Roller cams use this technique.

For instance, one cam's lobe looks 'pointy', so max lift +- 10% is realized for, say, only 20 degrees of rotation. (this is just an example!)

The other cam's lobe ramps up faster, then levels off to form a nice, wide nose on top. Max lift for this cam (+- 10%) is realized for 30% of rotation. Guess which cam makes more power?

[P10DET]

Originally posted by manzano
Average dyno gains on their pre-00 SR20 cams is 8 rw hp with no other mods

I'll bet you $100 they gain ZERO rwhp.

[P10DET]

Originally posted by manzano
...and they can squeeze another few ponies if they can take advantage of the roller rockers to add some more lift while keeping their 260 duration.

It's not likely the roller cams with gain more than the regular cams due to the lower redline of the roller engine.

[manzano]

P10,

No bet. How 'bout front wheel horsepower?

[P10DET]

Originally posted by manzano
No bet. How 'bout front wheel horsepower?

I won't bet against that. I'm sure they will get that. I've talked with Mike Kojima and he tells me the prototypes are already showing nice gains. They are still trying to get a bit more out of them.

[manzano]

P10,

Sorry about the RHP thing. I'm old, and get confused easily!

You figure 102 lb/ft of torque at the (drive) wheels at 6800 rpm is worth 132 wheel hp, which is 10-12 over all the (legit) baseline roller G20 dyno numbers I've seen. I wouldn't be surprised to see them get 105, which works out to be 136 hp.

[P10DET]

Originally posted by manzano
Sorry about the RHP thing. I'm old, and get confused easily!

Hehe. You're not the only one. If you're older than me, you can get as confused as you like. BTW, tell me when I start drooling, OK?

Originally posted by manzano
You figure 102 lb/ft of torque at the (drive) wheels at 6800 rpm is worth 132 wheel hp, which is 10-12 over all the (legit) baseline roller G20 dyno numbers I've seen. I wouldn't be surprised to see them get 105, which works out to be 136 hp.

OK.

Sounds like you're getting info from someone who is connected as well.

BTW, hp is a function of torque, but there was just a debate on the SE-R list how the Dynoject calculates hp. Rob Cadle thinks it calculates hp first and then converts to torque rather than the other way around like on a brake dyno.

So what torque figures are you quoting? Peak, or at max hp?

[manzano]

George,

Horsepower is merely a function of torque and RPM.

All a dyno knows is how much torque an engine is putting to the rollers. It then uses the following formula to calculate hp at each measuring interval. As far as where the engine reaches peak hp, it depends on how gradual torque declines after the peak, etc.

If you know how much torque an engine produces at, say, every 100 rpm interval, you can calculate the HP at the same engine speed. Then, just connect the torque and HP dots.

HP = T x N/5252

Since we are talking dyno, T will be torque put to the roller. H is horsepower, N = engine speed (RPM), 5252 is constant.

Knowing the SR20 engine with a cam will reach peak HP at or near redline, I worked backwards.

102 * (6800/5252) = 132 HP
104 * (6800/5252) = 136 HP

[P10DET]

Originally posted by manzano
Horsepower is merely a function of torque and RPM.

Yes, I know. I basically said that.

Originally posted by manzano
All a dyno knows is how much torque an engine is putting to the rollers. It then uses the following formula to calculate hp at each measuring interval. As far as where the engine reaches peak hp, it depends on how gradual torque declines after the peak, etc.

Not necessarily true.

The Dynojet doesn't measure torque like a brake dyno does. It is an inertial dyno that measures a number of things to calculate hp and torque.

From Rob Cadle on the SE-R Mailing List:

[COLOR=dark-blue]Actually, the dynojet measures the change in drum RPM over a (small) time step. Change in rotational kinetic energy is then calculated from known drum inertia. Work is equal to the change in rotational kinetic energy. Average power is work divided by time.

So, drum velocity is measured (actually, drum position is probably measured, and velocity is derived). Drum acceleration is not measured, nor does it need to be determined to calculate wheel hp.

Once hp at the wheels in determined, torque is calculated from:

T = HP*5252/RPM

Where RPM is engine speed. This is why you can't get a torque curve for the car if the speed pickup isn't connected.

(and pasted from another messge by Rob)

Alright, now maybe I'm talking out of my ass, because I haven't thoroughly researched this. I may be wrong.

BUT, I *think* that the dynojet calculate HP and derives torque from that. If the dynojet calculated torque first, then it would have no way to determine hp if you didn't have an engine speed pickup connected.

In fact, when you do not have an engine speed pickup connected, the dynojet gives measured hp, not torque. This is why I'm pretty sure that it is hp that is measured, not torque.
[/color]

Originally posted by manzano
If you know how much torque an engine produces at, say, every 100
rpm interval, you can calculate the HP at the same engine speed. Then, just connect the torque and HP dots.

HP = T x N/5252

Yes, I know.

Originally posted by manzano
Knowing the SR20 engine with a cam will reach peak HP at or near redline, I worked backwards.

Your assumptions are incorrect.

[pche059]

so manzano,
would you have any ideas if the redline of the roller rocker SR20 could be raise ? and how much higher if at all?

[P10DET]

Originally posted by pche059
so manzano,
would you have any ideas if the redline of the roller rocker SR20 could be raise ? and how much higher if at all?

So far JWT has not attempted it. All of their testing has been with stock redline.

[pche059]

oh my god...crappie
according to my S-AFC meter....my redline is at 6680rpm....any attempt to go over that will result in hitting the rev limiter....bounching like crap

well...i don't think i 6680rpm is enough for a 2L na engine?
what do you guys think?

and geo.. what are the different ways to increase the max torque figure?
if it can be improved at all?
and how much improvement do you think it can be obtained?