Tracking the 914 - Happy New Year!, Turning this into a regular thing... Options

[Justinp71]

@Justinp71

How are you tuning your carbs? For some reason the voodoo of “listening” for the sweet spot is lost on me. Since going to Aase, my car runs much better, but I still feel there’s much left on the table with some tweaking.

I have an afr logger I’m going to set up this week and I’ll post results for thought/comment here.

Any additional thoughts are welcome, but not expected till I get some data posted.

I went thru the PMO notes and checked for proper float levels, fuel pressures and then the air balance between each throat. Then I just do the idle adjustment how PMO describes where you go to each carb and look for the highest idle.

Once that was done I did some runs to WOT at different air temps and just looked down and recorded the different AFR's. Then adjusted my main jets appropriately. I had gotten initial carb settings from somewhere that were close, I just needed to change my main jets in the end.

In some temps (typically cooler) it runs perfect. When a little warmer it has a few flat spots, but I think that's typical. I'm actually working on installing the X faktory throttle bodies soon, but if I had a dedicated track car they would be unnecessary.

Some helpful tips-

http://www.pmocarb.com/installation_print.htm

https://www.pmocarb.com/Images/Instructions-3.pdf

[stownsen914]

AFRs will be a great guide to tune. The basic process Justin mentions sounds about right.

[infraredcalvin]

Thanks, I’ve just been overthinking it. Haven’t had a chance to install my LM2 for logging. I’ll post graphs when I do…

[infraredcalvin]

OK first graph, should be showing both left and right banks, but my LM2 was glitching and only recorded the right side bank. Regardless they're closely matched at the moment.

- Leaning out at higher RPMs
- Rich at cruise

I'll try a larger main jet and take another run...

[Justinp71]

AFR's probably go down when you shift from the extra pump on the acceleration pump circuit. Yes def need larger main jets, which makes sense for that beast of a motor. That will help make it feel like its not running out of breath on the high end. Looks as your cruise rpm came down to 4k then the idle afr came closer to 12:1 which afaik is as good as it gets for carbs. The problem with 3-4k cruise is the idle circuit and main circuit are typically both on for a smooth transition so cruise afr is always rich.

[infraredcalvin]

Increased Main jet from 140 to 150. Looks like that might have done the trick. Thoughts?



Current Carb Setup:

46 ida Italian Webers
Venturi/Choke: 42
Main Jet: 150
Air Correction: 170
Emulsion Tubes: F7
Idle Jet: 50

[Justinp71]

Cool, alot better (IMG:style_emoticons/default/piratenanner.gif) What's the butt dyno's opinion on the new jetting? I'm surprised how lean the low end is, does it transition good from idle circuit to mains?

[infraredcalvin]

All in all she feels good, no transition issues or flat spots just pulls nice though 6500, I’m carrying a lot of speed and making a lot of noise at that point so I don’t venture any higher. I’ll be out at ca speedway in early aug, there will be a dyno, so I’m going to try and get her dynoed before it gets too hot out there.

Still working on hood pins to keep the hood down, but will be looking at alignment next…

[infraredcalvin]

Can’t really tell you why it took a whole day to put 2 of these on… (IMG:style_emoticons/default/headbang.gif)

[infraredcalvin]

In for tech with younger brethren….



Headed to small Cars & Coffee tomorrow with a few buds, we’ll see what other hardware shows up…

[Justinp71]

Cool! Making progress... it will be interesting to see how the next track day goes.

The 718 is cool, you probably have more cylinders than him!

[infraredcalvin]

Favorite seat, Recaro SPG! I got it a hair lower and my arms a bit further from the steering wheel as I hoped. Also got some room putting the car in 2nd gear, old seat would touch shifter. All while still using stock sliders.

I know this seat is more comfortable than the Cobra, I was in and out of both seats several times, I couldn’t stand being in the Cobra more than 20 min or so. I fell asleep in the Recaro… a few times (IMG:style_emoticons/default/lol-2.gif)

[infraredcalvin]

A few shots from C&C, sorry not much variety in shots, my buddy’s GTL and another’s speedster , both have new motors and we’re out for a quick test before loading up for Monterey Historics.

[infraredcalvin]

Cool! Making progress... it will be interesting to see how the next track day goes.

CA speedway in Fontana this weekend, let’s see if she’ll hit 150!

Anyone want to venture a guess on dyno numbers?

I’m going to say just under 200 at the wheels…

[Justinp71]

Cool! Making progress... it will be interesting to see how the next track day goes.

CA speedway in Fontana this weekend, let’s see if she’ll hit 150!

Anyone want to venture a guess on dyno numbers?

I’m going to say just under 200 at the wheels…

Shoot you better be over 260hp, this 3.2 is what I modeled mine after and its 253hp at the wheels-

http://forums.pelicanparts.com/porsche-911...fore-after.html

[infraredcalvin]

Thanks, keeping my expectations low. I have no idea how she’s going to perform on the track. So much different feeling than my 930. I think it has alot to do with my alignment setup…. 930 is light and nimble, power delivery is an explosion though…. My narrow body race car (blue hood) felt very light , almost formula v light on 205s…. Was set up well. This car feels piggish… heavy, slow to rev (at least prior to last tune). I don’t like caymans pulling on me in the straights…. I’ll report back after first session….

[campbellcj]

Glad to hear you like the Recaro SPGs - I just got a set as well, about to replace some really old Cobra Suzukas that I actually like quite a bit too but are well expired and grungy.

[infraredcalvin]

Fun weekend, learned a bit more about my car. The bad news is with the motor, as expected, way low on power, dyno’d at 164 hp/189 tq. to the wheels. This jives with the old dyno sheet I found in the PO stash.



Check out how early it makes torque, this explains how I was able to pull out of turn 9 hairpin at CA speedway in 3rd gear when everyone else was complaining about having to go down to 2nd.

[slivel]

Looks like the mixture is getting very lean between 5500 and 6500.

[Justinp71]

Dang you are missing like 100hp... Sorry to hear your track day was less than ideal.

I would start with a compression check and leak down check. Almost seems like it has an air restrictor plate in it. Seems like to me not much air volume is getting in the motor. Would make sense the cams are out of time, burned valves or cam going flat??? Maybe search on pelicanparts and rennlist to see what you can find there too. Maybe call one of the known porsche engine shops like supertec and see what they think.

Alot of low end torque and low hp points to me as large displacement with low lift, like it has a stock 2.0 cam (like the old chevy motors).

How were the motor temps?

How does it feel heavy? Lots of body roll? slow to turn in?