Can anyone here fitting fuel injection tell me if Twin or Quad throttle body injection would work on a VW engine. I'm thinking of trying to develop a Quad set-up using the throttle bodies off a Corolla.

Adam.....

I had quad throttle body injection on my 1916 engine in my Manx...went very well...but the induction noise got the better of me so it now has a Subaru...

What throttle bodies did you use. The corolla ones are all that I have found so far and cost around $200 with manifold and injectors although I have to cut the manifold in half and re-tap the fuel inlet for another fuel feed pipe.

Have u got any pics of the Corrolla T'body ??

Your better off using a single throttle body they work better

using quads is a pain as you will spend more time adjusting and syncronising them

everyone i know who had twins or quads has gone back to a single set up even the guys with the quick drag VWs

A single throttle body will kill air flow on a N/A vw because of the manifold.

Boosed engine will loose flow too but it can be made up for with boost.
Most boosted engines have restrictive tubes between the turbo and engine either way so it will be less obvious.

that's what I thought..............my understanding is that twin throttle bodies would be better, although I have never run fuel injection, I would have thought the principles would be similiar as carbies.

Here's a picture of the throttle bodies off a 20v Totota Corolle engine.

I've found a set for $150 including throttle position Sensor. From the picture it looks like if I cut the manifold in half I can tap the open holes to take another feed pipe.

I ran a single with plenum, and went up to quad and the improvement was as expected, but certainly more induction noise.

I have quad throttles and they work great. They are off a K100 BMW m/cycle

I've also started looking at Honda 954 and Yamaha R1. What computer are you running. I only want a symple one. Most newer computers are too over the top for what I need.

have a look at my set up

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099 

Here are the R1 TB's. It looks like they can be split into pairs.

looks like it what about the fuel rail

I run a Gotech ECU ( http://www.gotech.co.za ) which is the cheapest around at about $400. It does everything I want spark, tps input, closed loop, logging direct fire etc. Howver I have sung its praises in the past on this forum and just copped flack for pushing it.

Mortgage your house and buy a Motec, Haltec or Wolf - I'll stick with my Gotech the whole system including injectors, throttle bodies, fuel pump, fuel rail and other sensors cost me about a grand all up.

My engine is NA but it can handle a boosted engine.

Ken

Thanks Ken. That would do all I need. It's not as if I need an ECU that can handle 50 different inputs.

which model gotech are you using Ken?

GOD DAMN - just finished typing a response and lost the lot

Try again,

Horses for courses.

For performance applications ITB (individual throttle bodies) are the way to go. That's why manufacturers like BMW only use ITB on their M-Power vehicles. Also why motocycles (light and rev to over 10,000 rpm) use them. What's interesting with the BMW M5 is that even though it uses ITB, it also has a plenum from which manifold pressure readings are taken.

On the other hand, for a daily driven application the single TB and plenum are able to be properly tuned using throttle opening (%) and load (MAP). You only have throttle opening on a ITB system. That's why 99.9% of vehicle manufactures use single TB and plenums.

The other issue with ITB on a VW engine is the linkage. When the engine is cold and the TBs are all shut, how far will they open when the engine warms up?

Just the basic one Gotech MFI

With my ITB's I just run a TPS sensor and it runs like a dream - idles at 650 rpm and revs out with no flat spots or hesitation. Starts first pop with no cold start set up and warms up very quickly.

So your system has the same ignition advance at say 2500 rpm at 30% throttle, regardless of whether its cruising or climbing a hill?

Yes - that's correct. That would be true if you had a map sensor - at 25% throttle and a set RPM the manifold vaccum would be the same whether you are cruising or climbing a hill.

It is well recognised that MAP-based tuning is a more accurate method of determining engine load. That's why all manufactures use it.

How does a TPS-based system differentiate between a free reving engine at 100% throttle opening and an engine under load (climbing a hill) at 100% throttle opening?

I'm not saying your set-up doesn't work, it probably works well. But there are better ways. The modern ECU can generally compensate for poorly designed systems.

Sorry but you need to think about it a little more.

The reason MAP based systems are used is to more precisely control fuelling during transient driving for emission control reason. eg over run cut etc. But for performance on a NA engine a TPS system is just fine. If it is a boosted engine then by definition you need to measure manifold pressure.

If you had 100% no load the engine would not be rev limited and self destruct. The only thing that controls the RPM at 100% throttle is the load applied. If you have no load and want to control the speed to say even 6500rpm you would close the throttle.

In either case a TPS shows 100% throttle and a MAP sensor would show zero vacuum.

Trust me for every day driving when you are not too worried about meeting emission a TPS system works perfectly fine and much better than a MAP based system with ITB"s. Most ecus can be set up for 100% TPS.

Ken