Different carb setup? - Page 2

911pcars · 10-16-2003, 12:27 PM

"I don't really like the max rpm part of the equation."

May I ask why? At some point, you will want to see if this setup either reduces, enhances or provides no power/driveability advantage over a factory setup. the "max rpm" part is when you want ...... max power.

Sherwood

TerryBPP · 10-16-2003, 12:37 PM

How do you know what your max hp is if your car has been modified or dynoed?

911pcars · 10-16-2003, 01:02 PM

Terry,
You just said it, "dynoed".

In lieu of an engine dyno or relying on seat-of-the-pants measurements, I'd suggest running a baseline HP/torque measurement on a chassis dyno first. Then install your new induction system and rerun on the dyno. Compare A to B, then draw your own conclusions. Also have the dyno shop record the A/F ratios during the testing. The chassis dyno can't test driveability as accurately. For this, just drive; perhaps some 0-60, 30-60 mph tests, idle, hot/cold starts, throttle response, etc.

BTW, not discounting the fact that the factory has made some mistakes, but don't you think Porsche would have used a less expensive carb setup if it improved the power and driveability over the Webers that were available then? There were several two-barrel Webers available they could have used if they worked as well, each tuneable with removeable venturis, jets and all. Except for emission controls, I don't think carburetor technology progressed that much since the 60's. Can you think of any other carburetor besides Weber that has removeable venturis, idle jets, main jets, emulsion tubes and variable pump stroke? Okay, PMO.

Maybe you should try 2-barrel Webers instead of Carter/Hollys should your initial tests show promise.

Sherwood

Early_S_Man · 10-16-2003, 01:09 PM

Terry,

It is well-explained in Bruce Anderson's Porsche 911 Performance Handbook ... that the 'max rpm' you cited is more accurately termed 'rpm at which peak power occurs' ... and that is simply a guestimate based on the camshaft profile selected, or from dyno data. The formulas have been used more than 40 years without significant problems ... whether you like them, or not!

Randy Webb · 10-16-2003, 04:13 PM

That looks a lot like the setup I put on my VW bus in the 1970's.

I don't see why anyone would put in on a Porsche -- the idle will be poor, the barrels can't be tuned for each cylinder and the intake runners are loooong.

TerryBPP · 10-17-2003, 09:25 AM

The intake runners will be about as long as MFI runners (2-3 inches and straight). I'm thinking of using Mikunis after some research. The whole purpose of trying out a different setup is to find something close to webers at a fraction of the cost. You can do alot of experimenting for the cost a USED set of webers and related hardware.

I think that carb technology has progessed a bunch since the 60's. Have you seen a Barry Grant carb?

TerryBPP · 10-17-2003, 09:37 AM

Something like this:

Schuey · 10-17-2003, 09:42 AM

terry, if this works and you can fab me an intake, sign me up as customer #1

Kevin

TerryBPP · 10-17-2003, 09:48 AM

For Sure Shuey.

dd74 · 10-17-2003, 09:50 AM

Yeah, Terry - damn the critics. Fight on, man!

MotoSook · 10:04 AM

What are you guys willing to pay for a carb setup that is NOT Webers or PMO's?

If you had the opportunity to buy a carb set up that is modern and very easy to tune, what would you pay?

I can't get into PMO's for less than $3000 for my car.

With that in mind, would you guys pay $2000 for a modern and new setup? (Used Webers might put me back $1000 at the end of the day)

dd74 · 10-17-2003, 10:04 AM

$2K? Not if it isn't EFI. $2.8K will get you a TEC3 run 3.2 Motronic system, and yield the same hp as PMOs.

MotoSook · 10-17-2003, 10:09 AM

Is that 2.8K for the TEC3, including the injectors, pickups, intake, etc,..?

So why is PMO still in business if EFI is so much cheaper and easier than PMO?

TerryBPP · 10-17-2003, 10:20 AM

And for the $1000 bucks they are still USED! You never know if they need a rebuild until they are on the car. Then thats another couple hundred. PMO's are so expensive you could go with MFI. But then there are still tuning issues. TEC-3 is awesome but noot pratical unless your racing. From what I understand there is a lot of mapping involed which takes hours and hours.

In a perfect world a japanese company (like Mikuni) would make a 3 barrel carb for use at a fraction of cost of PMO's. Why can't life be simple.

dd74 · 10-17-2003, 10:22 AM

$2.8K for everything, including TEC3 - at least that is my understanding.

Why is PMO still in business? Don't know.

Why'd the Red Sox lose last night? Don't know.