Group Buy: 3x8 Throttle Body Mod + Plenum Mod

Gosh!! I was just reading back a couple of pages..how did this happen? What does a car in a shop with dent in it have to do with throttle bodies?...

 

Mr. Sloan has no room to talk down to anyone, right Mr. transition consultant to the infamous bogus Exotic Car Warrantee Company. Something about those that live in glass houses rings a bell.

We are here to learn and experiment about our cars, not get caught up in
bickering BS, if this works great, if not it was worth a shot, many cars have had big improvemnts with CIS KJet with the Weber Big Bore TB kits, CIS provides plenty of fuel the problem is air restriction and delivery.

 

That's what I've been asking...is the CIS (K-Jet) problem air, fuel, spark, or timing? And you're saying what I think is obvious to observe in the previous diagram...that the CIS restriction/failure is air.

So how to get more air?

Porsche and Ferrari went with larger sensor plates than other users of K-Jet (110mm vs 80mm). Can even larger sizes be used?

Will a larger TB help? How about foregoing the OEM intake tube/airbox to instead use an airfilter mounted right where the intake tube previously sat?

 

Would there be *any* performance advantage to popping open the Auxillary Air Regulator at Wide Open Throttle?

Who says that the AAR only has to be for cold starts?!
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I am far from an expert on KJet but from what I have read it was designed as a performance fuel delivery system and has plenty of ability to provide all the fuel required the trick is to get more air into the engine which would be done via a larger TB.

 

I dont know about Mercedes doing so much better. The 560 motor makes about 230 HP, not a great deal for a engine almost twice the size of a 308. And this 380 is really a joke, only 155 HP. I have looked at the manifolds, and while that big ol sensor plate is right up on top, there are a bunch of convuluted passageways down underneath it to get the induction into the heads. I think its probably pretty restrictive too.

On your guys CIS cars, because those who have turboed them have not really had to fiddle with it, obviously the system can flow fuel plenty good. But there are probably to many other problems working against each other. The cams are really rediculous, from any kind of performance standpoint. Although, they could probably be dialed in to a different timing event by playing with a degree wheel. That hose coming off the CIS into that throttle body just looks rediculously small IMO, for anything thats going to make some power. I had a hose bigger than that on an old 1400 cc four banger back when I was a kid. If thats the case the 308 needs TWO! Two CIS units for a four cylinder could probably be adapted if there could be found some room, but then you might as well just carb it like Russ did and Enzo would at least be happy. Its certainly not stock, but its sure close to how they originally wanted the cars.

But going back to simple things, I think cams taken right up to where the CIS begins to get stupid, bigger throttle body, better exhaust, and maybe as Kermit has mentioned, looking at the other side of the fuel distributor, the air cleaner. Any restriction in a system already built restrictive is only going to get worse. If those things worked on all the other cars in the world, there is no reason to believe it cant work on a 308.

 

Could you delete the sensor plate altogether by tying the sensor plate arm to the throttle cable or throttle valve? Would that free up one restriction?

 

No Doubt,
great enthusiasm. mk_e has already explained pretty much the only way to hack the CIS to eliminate the restriction. The plate is the problem. Bigger isn't needed in this case, it's sized for the amount of air that will be flowed by the engine with the designed induction system. Removing that restriction would be really helpful but requires sensing AIRFLOW in another manner (not throttle position).

 

the 2.5 16 mercedez benz 190 has a similar injection system and makes 205 hp being a four cylinder 2.5 liter engine.

 

To give everyone an idea what you are up against with the FI on the 308's in terms of "out-dated" - aside from the O2 sensor - it's the same as used in the 77 VW Rabbit.

 

You can remove the air mass sensing plate and meter the fuel by throttle plate position. That is what was done on racing mechanical injection systems. It can be made to work quite well but has 1 key weakness, it can’t sense load. For racing it isn’t that important, since most of the time the engine is accelerating, they simple tune to an air/fuel mixture of about 12:1 for good acceleration and call it a day. For the street though, 12:1 is still what you what for acceleration, but 14.7 is what you want the other 90% of the time…and there is no way for the system to know when you want what without adding additional controls of some kind, whether mechanical or electronic like the mass air sensing plate. I guess another option would be to do something with rpm vs. throttle plate position; it would be complicated to do mechanically though.

 

Years ago I looked into Mods for the CIS System, this one still exsists. Links and description provided and it is only $52.00

I will let the experts decide whether it will work for the 308 as I never went farther then finding it.


http://www.autotech.com/tech_fuelinjection.htm

On CIS cars which do not have the Lambda system, the system pressure can be adjusted to optimize the cars perfor- mance. We recommend adjusting your injection to 5.4 bar system pressure by using our shim kit and fuel pressure gauge. Later model cars with Lambda work well leaving the Lambda sensor (oxygen sensor) in the circuit and rarely need to be adjusted anyway.

K-Jetronic Shim Kit

Within the CIS fuel delivery system there are two different pressure levels, system pressure and control pressure. System pressure is the fuel pressure that is sent to each injector, and is adjusted by changing the thickness of the shims in the fuel distributor. This kit includes enough shims to give you just about any system pressure you wish, as well as a new shuttle valve for your fuel distributor. It is necessary to use a fuel system pressure gauge to map your progress from baseline to the desired pressure. Not for CIS-E.
http://www.autotech.com/prod_engine_fuelinj.htm

 

I did a little looking really fast and found this:

http://www.chirco.com/cgi-bin/chirco.storefront/43b29ff003b3ef82273f4077201506ea/Product/View/CPR1319

You get 2 copies of weber IDF44 with 36mm venturi (they have 40s too) and manifold for $700. So for $1400 you get the 4 carbs you need. I’m pretty sure that for about $500 the manifold can be modified to fit a Ferrari. So for under $2000 you could do a nice carb conversion and pick up 20-30hp. If anybody needs help modifying the manifolds, let me know.

 

The IDF is a very tall carb and I doubt you would get it to fit under stock deck lid.....

The DCNF (stock) is far more compact.

 

And the 930 Turbo.

 

Okay, I know the system hasnt really been used alot since better designs came out, but what about a Hilborne type system? What these guys want, and I would want if I owned a CSI car, is something relatively simple, and rather inexpensive that would give the car some life. Like for fun, we put our heads together and see if we can do something for as little money as possible, that gives the greatest increase.

I know from earlier discussions that the system can handle more cam, but how much more? Inlet opening at 16 BTDC is not helping anything. Its not a wide angle cam, but swinging it 10 degrees should give some benefit I would imagine. What about the actual air filter assembly, and ducting into the CSI, is that holding up air? If the air cant get in in the first place, nothing done downstream will have much effect. Now back to the throttle plate. How large can that go before something snags? What would need to happen elsewhere, to increase that plate to 80 mm?

 

Sorry, looks like the exhaust cam could fall back an easy 10-15 degrees too.

 

Where's your faith

Still, no problem. Here's a pair of weber DCNF40 with manifolds - same $700. So 4 brand new webers for $1400.

http://www.cbperformance.com/catalog.asp?ProductID=1466

or how about 4 throttle bodies for EFI with injectors and fuelrail for $1050?

http://www.cbperformance.com/catalog.asp?ProductID=412

Add a $1200 haltech E6x and $500 for mailfolds and you've got a pretty cool mulit-TB EFI system for under $3000

 

a Hilbone type system is what I was talking about earlier. It has no way to sense load, it will give great performance and horible milage, or the other way around, but not both.

 

With the part of the deck lid I had to cut out ;-)
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How much did you miss by Paul? So is it the whole carb sticking out or would something like short stacks solve it?…something like ½ alum plate with a radius machined on or maybe with a drop set-up to put the air cleaner down over the carb?

I thing the GTS/GTS (the turbo version of the 328) deck lid already has an extra 1”-1.5” of height built in to clear the intercooler they added, would that solve it?

 

Mark,

I missed by far more then a inch, from everything I have heard the IDF's really require the tunned air stacks.
I also wanted to make sure I had air flow.
Better quit now before we get beat for hijacking

Paul
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Mark,

Please respond to my post #138 in this thread, I would be interested in your take on this inexpensive CIS Mod...I think Steve would be too.

Paul

 

Sure. They are basically talking about adjusting the air/fuel mixture, nothing more. The CIS car do tend to be lean from a performance point of view from what I’ve seen any way. Richening it from the 14.7 it probably came set at to 13.2 should add about 5 hp if I had to guess…but I’m not sure how happy the cats will be with that, they may need to come off. That would be true for a carb conversion too, but they’ll be fine with EFI.