TPS vs MAP - VW type 4 air-cooled

nosfera2 · Post by **nosfera2** » Mon Jan 14, 2008 11:55 am

I am hoping to be running MJLJ on a type 4 (between 1700 - 2000cc) air-cooled engine, with Dellorto DRLA 40s in my 1973 automatic camper. I am planning a road trip in the van, so simplicity in a roadside fixing situation is an important factor as much as ease of installation and robustness.

I have done some research, but am no clearer on which of the 2 would be the better option.

TPS:
I phoned a local Webcon dealer (as suggested on here somewhere) who says there is no TPS available for DRLAs. Can something be modded to fit?

MAP:
Much of what is discussed on the forums is for side draught carbs, does the down draught make any difference?
My current distributor gets its vacuum from the left hand carb, it's an advance only dizzy. Would that (with an anti pulse valve) suffice for a vacuum signal? The other option would be to tap the tube that supplies the vacuum to the auto box and the brake booster. It runs from manifolds 1 & 3, almost like a balance pipe.

All advice gratefully received.

Gilesy998 · Post by **Gilesy998** » Mon Jan 14, 2008 8:22 pm

Your last option would be far and away the best bet. I guess that the DRLAs are single-chokes each? If so the vac tube you mention would be the perfect place. If this produces problems, tap into each runner individually, route hoses to the vac reservoir and from there to the MAP sensor.

britlude · Post by **britlude** » Mon Jan 14, 2008 11:28 pm

i have dellorto drla 45's on my engine, i rigged a red ford TPS on the end of the throttle shaft, well more accurately there's a slot cut into the spindle end washer which the tps arm locates into

i'll post a pic when I get one... working the map for 8 inlet runners was too much like hard work for my application!

nosfera2 · Post by **nosfera2** » Tue Jan 15, 2008 2:22 pm

Gilesy998 wrote:Your last option would be far and away the best bet. I guess that the DRLAs are single-chokes each? If so the vac tube you mention would be the perfect place. If this produces problems, tap into each runner individually, route hoses to the vac reservoir and from there to the MAP sensor.

My Dells don't have chokes, but then my understanding of a choke is to help with cold starting? Somehow tapping the vacuum tube that currently supplies the autobox and the brake booster is my preferred way too. I know where I stand with vacuum.

nosfera2 · Post by **nosfera2** » Tue Jan 15, 2008 2:24 pm

britlude wrote:i have dellorto drla 45's on my engine, i rigged a red ford TPS on the end of the throttle shaft, well more accurately there's a slot cut into the spindle end washer which the tps arm locates into

i'll post a pic when I get one... working the map for 8 inlet runners was too much like hard work for my application!

Are yours twin carbs? Or a single? I did read about TPS being "made to fit". A pic would be most helpful if you can post one. There is something to be said for an elegant/minimal solution as well.

britlude · Post by **britlude** » Tue Jan 15, 2008 5:17 pm

twin carbs/single...? err twins..... errr 4 of them!!

'choke' is often refered to as the actual venturi 'choke' within the carb, not necessarily the choke enrichment system used when starting from cold! for example a 45 carb like mine has 36mm chokes in it!

the tps unit I got hold of (off a ford fiesta, focus or puma, I can't remember!!!!) has a lever actuator at the end rather than a d-slotted hole. made up a simple mount and dremmel'd a slot in the staked on washer on the carb spindle.

anyway, a picture tells a thousand words, so here's three thousand words worth...

nosfera2 · Post by **nosfera2** » Wed Jan 16, 2008 1:39 pm

britlude wrote:twin carbs/single...? err twins..... errr 4 of them!!

'choke' is often refered to as the actual venturi 'choke' within the carb, not necessarily the choke enrichment system used when starting from cold! for example a 45 carb like mine has 36mm chokes in it!

the tps unit I got hold of (off a ford fiesta, focus or puma, I can't remember!!!!) has a lever actuator at the end rather than a d-slotted hole. made up a simple mount and dremmel'd a slot in the staked on washer on the carb spindle.

anyway, a picture tells a thousand words, so here's three thousand words worth...

LOL. I could possibly mean carb bodies?

I have 2 separate carbs, on either side of the engine (it's a flat 4). Similar to this ->

Each carb has 2 venturis, like this ->

As an understatement.... that is QUITE an engine! Ta V much for the 3000 words, much appreciated. A motorbike TPS was suggested to me as well. Will see what I can find and mod as the MJLJ board I bought is already setup for a TPS.

britlude · Post by **britlude** » Wed Jan 16, 2008 6:38 pm

there is no reason why the TPS HAS to be on the carb, it's designed to tell the MJLJ how far the throttle is open, but as it's calibrated by software the TPS can be anywhere as long as it's connected to the throttle somewhere.... so, pedal, carb, or in the VW configuration, it can even run off the throttle crosslink bar.. just a thought!

nosfera2 · Post by **nosfera2** » Wed Jan 16, 2008 10:58 pm

britlude wrote:...it can even run off the throttle crosslink bar.. just a thought!

Glad you mentioned that, because initially I thought that might be the logical/easiest place to put it. All my research indicated on the carb was the way to go. I'll have a think about it. See what I can come up with.