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Jaguar 0.7 alpha build for 1972 VW Karmann Ghia 
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You don't *need* idle control, but not having it is a pain in the arse. PWM can easily be supported, stepper takes a little more work. DBW throttle is another option if you're feeling adventurous and don't mind building special hardware to drive the throttle. Then you can do idle control using just the throttle.

Size wise, small could be restrictive, big could be touchy torque wise at lower RPM, around 50mm or so is not a bad place to be. I have 70mm on my 2.0 and previously 1.8l engine. It's fine, easy enough to drive, etc.

TPS is certainly a good idea. At the least, for data, and soon, for actual fueling corrections, too. I take it that you are planning a common plenum setup? Probably a good choice as tuning an ITB setup on a VW flat four is likely a bit of a pain in the arse, too.

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Fri Jul 17, 2015 8:39 am
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LQFP112 - Up with the play

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Ok, so looks like I don't a TPS, but need the idle control valve. I'm thinking my wife will complain about the car dying on cold startup. The VW carb has a bimetal strip that is heated on startup. It keeps the throttle closed (choke) and the idle air circuit open. It is basically a timer. I assume I don't need a choke since AFR is controlled by the ECU.

I found a 46mm throttle body with TPS and idle control valve. I might get that, but I'll look around some more.

A common plenum? Just one throttle body for all four cylinders. The two pairs of cylinders are separated by the crankcase so I think the tubing itself acts as plenum volume. I want just one in case I go turbo. I went to bigger cylinders on the engine for 1.9L, but didn't change the valve size, cam, or crank stroke. I'm not sure if that will give the performance I'm aiming for, but I will find out soon enough!


Fri Jul 17, 2015 1:30 pm
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LQFP112 - Up with the play

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I bought the 46mm. It was in good condition, not bulky, had a TPS sensor and IAC valve. I looked at a throttle body sizing calculator and 46mm looked fine. It was the best deal for $25 shipped. I can always upgrade if I feel like it down the road. Settled - now onto other things.


Fri Jul 17, 2015 3:30 pm
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LQFP112 - Up with the play

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Made a spring compressor because the HF one I bought was crap and all the VW places wanted over $100 for theirs. It works great. I lapped the valves on one of the heads and now they all seal unlike before.

Image


Fri Jul 17, 2015 7:44 pm
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LQFP112 - Up with the play

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Finally got done entering my Mouser order for all the Jaguar stuff. Man, it takes forever to do, especially since not all the same parts are carried as Digikey. At least I have that part of the project rolling....


Fri Jul 17, 2015 11:50 pm
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Correct, no choke required, though out of habit I still try to find one on the dash :-D

http://www.sdsefi.com/9124to17.jpg
http://www.sdsefi.com/3821rotax.jpg
http://www.sdsefi.com/thomas18.jpg
http://www.sdsefi.com/edge115.jpg
http://www.sdsefi.com/edge119.jpg
http://www.sdsefi.com/edge121.jpg

Not sure if I can hot link to those images, or not, but if not, they all came from here: http://www.sdsefi.com/rotax3.htm

Runners can't really act as the plenum. You definitely want a decent volume behind the throttle, and you want it evenly arranged to avoid funky resonances. You will also want to tap your MAP point of wisely, and by that I mean centrally/symmetrically for most consistent pressure.

I reckon not ordering a kit from Andy is a fail, and I think you just found that out. I found that out years ago when I didn't order a kit from some other clowns and sourced all of the parts locally. I may have saved 50 or 100 bucks, but it wasn't worth it at all, even considering I had little cash.

Nice work on the valve spring tool! :-)

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Sat Jul 18, 2015 5:38 am
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LQFP112 - Up with the play

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Quote:
Correct, no choke required, though out of habit I still try to find one on the dash :-D


:lol2:

It is interesting how the aircooled VW engines have no plenum. When they use the dual carbs, the distance from the valve to the carb is pretty darn short. This pic is also along the same line as your examples plus the stock intake.

Image
Image

The stock engine is pretty heavily restricted on intake. It is not meant to rev that high. Because of the restriction, they have their torque down low in the RPM range.

I'll have to do some more research on intakes and plenums to figure out what I want. If I'm going turbo, I'm not sure how critical each of them are....but I just want to get this thing running again. The turbo can wait.


Mon Jul 20, 2015 3:33 am
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If the two cylinders on each bank fire 360 degrees out from each other, then you could also run two small plenums above the heads with plumbing to them from a single throttle or dual throttles + a balance tube. Lots of ways to skin this cat, but ITBs are a pain to tune, so avoid that is my advice.

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Tue Jul 21, 2015 12:22 pm
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LQFP112 - Up with the play

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The two cylinders on each side are 180 degrees apart.

I made a spreadsheet for Helmholtz resonance so I'll have to pick an RPM to aim for and adjust runner length/diameter and plenum volume to fit. I didn't want to bother with it, but should be simple to implement. I'll use 1.5" diameter runners and see what length I need to get them all together. Then adjust plenum to get RPM goal...2500-3000 RPM?

You mentioned putting the IAT sensor at the fan, but shouldn't I put it between the throttle body and the intake? Especially if I go FI? I would think I would want to account for compressed air temp. Should the IAT and MAP be measured at the same place? Seems like you would want to so that you'd know the exact amount of air coming in.


Tue Jul 21, 2015 1:48 pm
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LQFP112 - Up with the play

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That editing thing.... :(

Also, I realized I need to get coils. I apparently only bought an igniter. I guess I need to read up on it more. Any suggestions? COP would be nice, but I'd have to mess with the board and coding. Do I need to get 2 coils for wasted spark then?


Tue Jul 21, 2015 1:56 pm
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