Single point injection carb replacement

[Paul H]

Just working on a single throttle body with single injector to replace the stock 34 pict carb.
I have the 42mm prototype built and ready to test on a 1904cc engine with C35 cam.
It's was a tight squeeze getting the TPS to clear the alternator and getting the correct angle on the cable but it's done and accepts the VW air cleaner box.
Anyone interested in this ?

[gtmdriver]

That's the set up I did on mine.



I used a BMW 1200 motorcycle throttle body on a T shaped inner manifold with the outer OEM manifolds modified to take the injectors.

[Clonebug]

Just working on a single throttle body with single injector to replace the stock 34 pict carb.
I have the 42mm prototype built and ready to test on a 1904cc engine with C35 cam.
It's was a tight squeeze getting the TPS to clear the alternator and getting the correct angle on the cable but it's done and accepts the VW air cleaner box.
Anyone interested in this ?

It sounds like an excellent way to get into FI at a lower price point considering that most stock carbs and distributors are worn out and give nothing but trouble.
Just look at the posts on theSamba........

What ECU are you going to use to drive the injector and what injector are you using???
You will need at least a 45 lb./hr. injector and possibly up to a 60 lb./hr. injector if you are aiming for 85 hp and up.

I like it!!!

[Paul H]

The motor with ITB 45s was 130hp so I got a Siemens 80lb/hr HiZ injector although I expect to loose 30hp so a 60lb/hr would probably do the job. I've got a Bugpack manifold to take a single IDF TB so I'll try that as well while I have the end castings on

[Marc]

Years ago when I was wrenching for USPS and was real savvy on the pre`94 GM TBI, I thought about applying it to an ACVW but never got around to it before they came out with a port-injected system and I lost interest in the TBI.
I figured that the components they used on a 2.5l Iron Duke should have the capacity to support a 2-liter at the RPM you'd turn a mild street motor (a good match for a Bus, say). The system "learns" as you drive; if you spend a lot of time with your foot in it the map shifts richer over time, or if you're a feather-footer it'll gradually trim the fuel delivery to the bare minimum to improve mileage.

The GM system uses a crank position sensor in the block (a trigger wheel is incorporated into the crank) which one might be able to fake using the VW diagnostic TDC sensor and a lot of dowel pins in the flywheel, but I probably would've gone with one mounted at the pulley to make it easier to tweak.

One concern I had was that while there's enrichment upon accel in response to manifold vacuum drop it might not be enough with the remotely-located injector and you'd end up with a bad flat spot and need to have an auxiliary injector to act as an accelerator pump (and you'd still need manifold heat, same as for a carb) - so I'm curious about how your setup works on that score.

[sideshow]

I've considered using a GM TBI or CFI shower head inside an old Bugspray (its missing a few bits that prevent it from working as Holley intended) just to mess with people. Lucky for me I don't have anything that would accept a stock looking Bugspray due to engine compartment height.

I think there is room in the market for that middle step between what a 34 PICT will feed well and dual carbs. Anyone know what the limit of a stock dual port center section is?

[Paul H]

We're going for ultra simplicity on this one and as most of the parts are already made for other applications then it was just a case of figuring out the throttle levers and return spring. Unfortunately the TPS we use with a clockwise rotation is no longer available but there is an alternative.
With regards to cold start,accel enrichment the single point will not be as good as a four injector but these engines ran with a crude carb just fine so with engine management it can only be better and unlike the stock carb it can be tuned for larger capacity , aftermarket camshafts and of course turbos

[Paul H]

Here's a pic

and one on the manifold

[Jadewombat]

Great stuff. Simplifies not have to take the top end apart and will roll in a lot of owners who would otherwise be hesitant about doing too much modification to the car if they ever wanted to go back to a carb. Just add crank-trigger and the 1930s ACVW is suddenly updated 70 years worth of technology and control.

Do you have some mileage/acceleration numbers with the carb. (pre-injection)?

[andy198712]

i think its a great idea!

[SC3283]

great looking and great idea...my only concern is, will the same problems that the single carbs experience occur here?....(working heat risers, hot air inlet)

[Paul H]

I got everything bolted down and just need to hook up the fuel lines,injector and TPS then on to the dyno.It'll be tested under worst case scenario- No heat riser ,no warm air pickup,cold damp weather.

[sideshow]

I like the packaging, is the open looking hole a placeholder for ported manifold vacuum or for an external fast idle contraption?

[Paul H]

It's just a 1/8npt port which can be used for whatever you want .
Just finished the mapping and dyno work and it tuned in real nice-I'll post up the results, video and graphs later

[Paul H]

Here's the power graphs-all of them


1904cc with Scat C35 cam and 044 40x35.5 roundports 1.5 inch merged header w dual mufflers

Maximum power without the belt was 103 at the flywheel which is probably the maximum you'd ever get from a stock dual port manifold, it just starts to become restrictive at above 4500 rpm but good torque from 1500 rpm to 4500rpm and over 120 ft/lb from 2500 to 4500

Heres the video


And a pic with the stock air filter fitted