Let's Play - Predict the HP Game!

[rdane]

This is an interesting comparison on carbs and CIS. Not directly related to a 3.0 but interesting none the less I think.

http://forums.pelicanparts.com/showthread.php?threadid=188800&highlight=iris

John, care to comment on induction and cams on the cars mentioned? Be interested in your take on the data repeated there.

[al lkosmal]

178.5 rwhp

[jluetjen]

rdane; I'm reserving comment until the contest is over. There's money on the table!!!!

[Plavan]

I say 207.5 HP. I'm psychic

[kstylianos]

I'm really hoping the carbs give more than 5hp also.

I have a very similar setup 82 SC 3.0, 9.7:1 CR, SSI's, and Elgins SC330 grind. Pulled 186 HP, 187 TQ at the wheels.

Considering the Webcam 20/21 is a bit hotter than the SC330 (and the 964), its intended to move the HP/TQ curve up in the RPM range. CIS really can't use all of this cam as its airflow is limited at high RPM. Carbs hopefully (if jetted correctly) should rectify this problem and provide a strong pull all the way to redline.

I do agree though since are using PMO's, you could have gone hotter with the cam (retard the timing a bit to avoid p/v interference).

205 hp @ 6500rpm.

[Aplha1]

My estimation puts this bad boy at 208 HP. Just an estimation on my part.

[camgrinder]

196 rwhp

[KobaltBlau]

I know you're not asking for this, but think about how much it would cost you to get nikasil 3.0 cylinders or bore&replate 3.2 cyilnders to 98mm, and buy JE 9.5 or 9.8:1 pistons with lots of valve clearance to suit. Keep the webers, but put in some cams in the GE40-GE60 or "Mod S" range. These mods would make a substantial peak power difference vs. your spec.

This ain't cheap, but going to 6 throttles (Webers, for example) doesn't buy you that much unless you also go to big cams. Of course you should also consider your intended use, because the "power band" for these engines is different. I personally think these cams (particularyly toward the milder end of the spectrum I stated above) could still be very fun for street use, particularly in a light car.

Just my $.02

[TonyG]

KobaltBlau

The thing you have to understand is that I just rebuilt the engine (which included replacing a lot of hardware just so that it was new... example all the rockers and rocker shafts, elephant foot adjusters and more...) to the tune of about $6000

$6,500 - Engine Rebuild (including some misc crap)
$3,000 - PMO Carbs/Manifolds/Linkage
$ 900 - SSI Headers
$ 800 - Web Cams
$ 350 - Muffler
$ 200 - Misc Oil Lines to back date exhaust
$ 300 - Rebuild / Recurve Distributor
........
$12,050 (plus a lot of other little expenses that add up...)

I just couldn't see spending another $3,000 to be able to get a slight increase in displacement, and be able to run larger cams, which would maybe make another 25rwhp (maybe it would have made more... but not in the rpm range I want to operate the car in, on the street).

It's still a street car. And even though I do about 4 track days per month (in various cars.. which will include this one), I still want to have it fun to drive on the street, and not evolve the car into a track car with license plates (as I've done so many times in the past....).

What I really want is smooth power, a nice TQ curve, and the engine to pull to 6000 - 6500 rpms before it rolls over. If I get that, and make at least 200rwhp, then I'm in good shape.

Lastly... the CIS setup is horrible on the track simply because it has no throttle response. I don't understand how people could drive a car like this fast on a track with the lack of throttle reponse that the CIS provides... it's horrible on the track.

And... by the looks of the tortorous air intake path that the air must travel in, up, down, around, pushing a spring loaded plate open, in a funky plenumn, then through the runners... can't be helping the engine breath up top. I know that a good set of carbs has got to be worth at least 15rhwp over that of the CIS.


In short, what I've tried to do was to put together a nice mild engine package with all the components matched and working together. I might try to squeeze in larger cams in the future though depending on what the dyno chart looks like.



So.... I pick up the engine tonight. It will be installed tomorrow. Then it's time to go strap it to the rollers and see what she'll do... mu ha ha

TonyG

[rdane]

CIS? Guess that depends on the car and the mods. SSIs and a 20/21 cam will wake up a 3.0 CIS car. Not PMOs for sure but not all that lacking either IMO. See my new post on the WRX STI I ran into this afternoon. You can judge throttle response of CIS and the value of a 3.2 upgrade a bit from my comments

[TonyG]

rdane

I read quite a few of your posts, all informative for sure, but I don't see where you really comment on throttle response.

I have quite a bit of experience with carbs (on Datsun 510 and 240Z race cars where we use one throttle per cylinder) as well as a ton of fuel injection experience with very high Hp Porsche 944 turbos (close to 500HP cars). And in my opinion... nothing even comes close to an individual throttle body setup with respect to throttle response. It's night and day different than a single butterfly/plenumn setup.

It's this type of throttle response that can make a huge difference when driving the car at 10/10ths on a race track (plus it's more fun on the street too).

So will the carbs make more power? We'll see. But I know that the throttle response will be much better without question (the same goes for individual throttle FI setups).

TonyG

[jluetjen]

rdane;
Have you ever driven an MFI'd car -- preferably a larger engine'd one like a 2.7?

[rdane]

Tony, I am happy with the throttle response I have in my street car. Ran the 3.0 some on the track and wasn't disatisfied but no question there are better answers to performance that CIS.

Like you my first priority was a street car so I haven't been unhappy with what I built. Grady has the right idea thought we all need a couple of engines to swap out as our thoughts change. CIS seems OK but then I don't know any better. Only carbed cars I have driven were V8s.

Noah says his new EFI is much, much better for throttle response than his CIS was. Even BA says carbs give you 10hp but it will feel like 50

20mpg is bad enough the way I like to drive. I just couldn't swallow 10 mpg or less that some of the guys see from carbs.

I am really looking forward to seeing your dyno sheet. Keep up the good work!

[TonyG]

rdane

You can tune carbs to produce fairly good mileage.

The key is to install a wide band a/f ratio gauge so that you can properly tune/jet the carbs so that you're not running rich (or lean) under cruise conditions.

Lastly, I might have to gear up (taller) the transmission so that I don't end up driving on the primaries while cruising, since the SC gearing is so short. And... I had already planned to install a much taller final drive ratio in the car anyway since I don't like cruising at 4000 rpms at 80mph (approximate). It's this type of scenario that will kill the mileage.

I plan to gear the car to turn around 3000 rpms at 80mph. That's my next project after the engine project, then after the installation of my 993 interior in the SC ... too many projects :-)

TonyG

[TonyG]

...:::ATTENTION:::...

GET YOUR BETS IN WHILE YOU CAN :-)


Here's the engine...

Completely assembled, ready to install!

WooHooo!!! (I'm happy)



TonyG

http://www.tonygarcia.org/911SC

[TonyG]

...::: UPDATE :::...

Engine installed and car running. It appears that the PMO carbs are very close with resepect to jetting and setup out-of-the-box... I'm going to get my wide band a/f ratio meter installed then do the final tune.

Initial impressions... wow... what a difference!

The 321 stainless 2 in / 2 out muffler by mb911 (a fellow pelicanite) sounds awesome. Made me want to get on a race track ASAP!

The car now pulls cleanly to 6500rpms+ (I let up at 6500rpms because I'm not sure how high to take it with respect to the strength of the factory 911SC rods/rod bolts. It easily pulls another 1000 rpms up top over that of the stock SC setup.

One problem though.... I sorta felt that the full throttle feel of the throttle linkage felt funny. It never really had a "clean" stop to it. And.. as I suspected, the throttle linkage was binding, causing the car not to have full throttle by about 15% It appears that the rod end of the "cross bar" is hitting the a/c compressor at close to full throttle. I'm not sure how to fix this just yet. I might be able to get a cross bar with 1/2" shorter arms, or a longer a/c belt (to adjust the a/c compressor out of the way). But.... there's more power to be had!

The dyno session is going to get scheduled for next week so long as I can get this full throttle clearance issue figured out with the linkage.

Lastly... throttle response. It's a night-and-day difference over the stock CIS setup. I'm sure some of it's attributed to the SSI/muffler/cams... but it feels very responsive, especially above 3500 rpms.

End of update...

TonyG

[rdane]

Hey Tony what is up? Looking forward to seeing your numbers from the Dynojet.

You have me thinking about the PMOs now since the most recent electromotive fiasco luckily fell through..

[Brother]

188

[smestas]

Im guessing 215

[KobaltBlau]

Originally posted by TonyG
KobaltBlau

...

In short, what I've tried to do was to put together a nice mild engine package with all the components matched and working together. I might try to squeeze in larger cams in the future though depending on what the dyno chart looks like.

TonyG

Tony, everything you said makes sense. I wasn't sure how far along you were in your process and I just wanted to share an alternative, but I think you made great choices. Sorry for my delayed response, I haven't been on too much lately.