EFI? or fix my Webers?

[cstreit]

Gang,

In the horns of a dilemma here. As I've annually improved the performance of our racecar, certain problems inherent to Webers have gotten worse. Namely:

1. Ability to properly tune: Without extensive dyno time and many purchases of jets, etc... I just can't seem to settle on a good fuel curve with these. They're close at times, but even the best I could get still leaves me in the rich or lean side above 5500 RPM. Far enough off that the car isn't running right, or safe (14.8:1 or 11:1)

2. The left-hand lean: I'm hitting 1.5-1.6 G's in some turns. THe fuel sloshes away from the float bowl pickups on the lefts and the car feels like it's on 4 cylinders. Kills my drive out fo the left hand turns.

So looking for objective opinions on my two options as I see it:

1. DO the Jerry Woods baffle modification to help the left-lean problem (does this work even for LONG hard lefts?) and continue to spend time on the dyno? ...with the assumption that changing conditions in the air (humidty, pressure, etc..) will still impact my performance

2. Convert to EFI and sell my very nicely ported/maintained Webers and Electromotive twin-plug to help fund the project?

[Shuie]

EFI. Please post details.

[jwetering]

The Jerry Woods mod is easy, and if you have enough fuel flow should solve the starvation problem even on long turns.

As far as jetting goes....that's a time issue more than anything I'd think. I can imagine tuning EFI will be as much hassle, or dare I say more?

Good luck.

[edbaus]

Chris,

What efi are you thinking of.

Believe me, if excessive dyno time is your concern, then efi will not help that. The innovate wideband that I installed just before the runoffs is definatly helping my tuning, but I have not been able to get the analog feedback signal to work properly.

Of course, I am throwing in boost with the deal too.

Ed Baus

[gumba]

I would try Bieker Engineering in Oregon for the float bowl mod (less expensive) It will take care of the fuel starvation problem. I went with the Innovate LM-1 to tune the webers. In the long run it's cheaper than dyno time (you can always sell the LM-1 when your finished). I then added 2 LC-1 wide band sensors (one in ea. header) connected to a dual a/f gauge that replaced my clock. The other option would be to run an LC-1 on one side and an LM-1 on the other. You can connect them together, I also do this. It allows you to record the session, then download into a laptop. You could check the a/f around the track and through the corners. I'm typically between 12-13/1 in the higher rev range, 4000-7000 rpm, and 13.5 @ idle.
I had a carb fire sometime back. Melted the secondary venturis and one pump jet. I had the carb cleaned and checked out, the guy said it was fine. After I got the motor running it had a constant miss. I noticed on the a/f gauge that the a/f was the same on idle, but as I starting bringing the rpm up the left carb (fire damaged) would start to go lean, 17/1. At that point I figure the LC-1's had paid for themselves.
Some of the Weber stuff is no longer available like the secondary venturies (I'm having Bieker make me a set), pump jets, and few other items.
I also thought about going to EFI for the above reason. I was looking at the Electromotive system through Clewett Racing, about $6000 +CA tax, set up & dyno time, somewhere slightly less than $7K. Since I'm already set up for Webers I would go with the PMO's if I need to replace the Webers.
Harold
3.4 twin plug, Electromotive HPV-1 & 46mm Webers.

[911K]

Originally posted by jwetering
The Jerry Woods mod is easy, and if you have enough fuel flow should solve the starvation problem even on long turns.

What is the Jerry Woods mod? I am having this same starvation issue with my Webers.

Thanks,

Mike

[Elombard]

What about PMOs doesnt that fix alot of that. I suppose they are not any easier to tune.

[Brother]

The Jerry Woods mod is shown in the 911 performance handbook. It is just a bit of sheet metal epoxied in the floatbowl to keep some gas closer to the pickup when in a hard turn.

[911K]

Originally posted by Brother
The Jerry Woods mod is shown in the 911 performance handbook. It is just a bit of sheet metal epoxied in the floatbowl to keep some gas closer to the pickup when in a hard turn.

Thanks! I'll get the book and check it out.

Mike

[gumba]

JW mills a shelf in the bottom of the float bowl then epoxies the plate in. Not sure how Bieker does it. I've had this down to two sets of 46's. One set by JW and the other by Bieker. The photo is of the JW's mod.

[911 tweaks]

Gumba,

I am looking for info on the dual a/f metering set up you did. Can you either PM me or respond here with the parts, where to get them and any pictures of your set up and how you set it up to monitor a/f for both banks?
I would greatly appreciate your help!!
Bob

[mb911]

chris,

Not a fan of carbs ever since I converted to EFI. I will again(I know I did last week as well) suggest megasquirt(bitz programed controller) and ITBs . You can do this for the cost of you selling your carbs and you could go MSII if you thought you may want to do EDIS in the future.

As far as tuning I can help you with this and set you up with some dyno tuning locally(oh yes the famous inaccurate dyno)

I am a big fan of carbs for what they were but If I were racing there is no doubt EFI.

I have a very good friend who drag races who has a about .5 mil in his cars and use to swear by carbs but those days are gone. Infact he even has an engine dyno that goes to 2000 hp so we could set your efi up there with the correct adapters..

[gumba]

911 tweeks: Westach http://www.westach.com/ made the gauge for around $190. I took a clock housing cut out the back and mounted the a/f gauge inside. I used 2 LC-1's from Innovate for the wide band sensors, around $200 ea. I plugged the LC-1's into a laptop to calibrate the sensors to the gauge. PM me if you want anymore info.

[cstreit]

Wow, lots of good information here, thanks to everyone...

Ben... I'll give you a call here this week so we can talk. Cost is a deciding factor..

[beepbeep]

EFI by all means. You could keep your Electromotive ignition and use EFI for fuel only. The very cheapest way is to use MegaSquirt.

I just bought assembled MegaSquirt II for 370$ and picked up EDIS coils and module on junkyard for 30$.

It doesn't get cheaper than that. You could even remove then innards from your carbs and use them as makeshift ITB's.

Regardning tuning: LM-1 with AuxBox is all you need. It has accellerometer and can log RPM vs. accelleration. Accelleration is directly proportional to torque and power is torque x RPM. With other words, you have your own pocked dyno. It won't give you the figures but it will allow you to tune for max power, whatever it is.

[cstreit]

Yah I understand the Megasquirt itself isn't bad, but then add all the injectors, fuel rails, ITB's, Wideband O2, etc.. and the costs seems to go p exponentially...

[jpnovak]

Chris,

I have the exact left-hand turn problem you do. I have accumulated all the stuff to go EFI. It will be a MS-II box. I only need the wiring harness, CHT thermistor and a new fuel pump to begin the swap.

My system iwill be a set of 46mm TWM ITBs. I will port my weber manifolds to match and use the existing linkage. I bought some used injectors, cleaned and flow matched a set of six. Now its just a matter of wiring it all up.

Go efi. This will make any future motor upgrades easy to deal with. There will be a learning curve up front but the performance should be worth it to maintain a good AFR throughout the rev range.

[Brother]

Does your race class have any rules on the subject?

[911 tweaks]

Gumba, I want to email you or call you but you dont receive any pm's. Please pm me so I know how to contact you. Thank you Bob

[gumba]

911 tweeks I pmed you.