Dual carb set ups - ?

[Os7213]

HaHa now i understand ty
Oh almost forgot here a little link for weber ajustments:
http://www.piercemanifolds.com/tech_spec.htm

hope that help
Ugo

[BenR]

eight-six Wrote:Dont think any flaming is going - just happy to get some views on this so all constructive opinions appreciated.

Quote:Eightsix: the timing map sometimes becomes constant or smooth at high rpm, with a fixed max.advance..however big cammed engines can have very irregular VE maps with large fluctuations between 4000 and 8000rpm..you need to adjust your timing too them...maybe just ask Ben what he does for timing and what difference he expects..he probably knows from experience.

I have dropped Ben an email, but havent heard back yet. If I can increase the power by having the timing set properly then fantastic just means I am quicker on track. The car performs well on its current set up, but I know its not perfect. Just want to make an informed descision on which way to go.

Quote:160hp on poorly adjusted timing sounds like 300deg cams and 1200rpm idle. Would be very very difficult to make that kind of power with the stock rev.limit. Get it on a rolling road some time and before that post some vids...carbies sound great.

Its got 288 cams, head skim, idle is lumpy and high. Goes nicley and sounds amazing - taking it to about 8k but pulls beyond and power is stillclimbing. I should have some video footage shortly.

I have no email, please expand on the problem?

[eight-six]

Hi Ben,

Sent you a PM through the DW site, which may explain why you haven’t seen the message.

No real issues as such, just wanting to tidy the car up and sort out the wiring – work out what part of the loom I do need and what parts I don’t.

The issue was I was unsure on how carbs on EFI works and was trying to get some information so I could work out how mine is currently set up and change it for the better. From some reading and the help of guys on here I suspect my timing is locked out and it may be the case that the car is down on power. It performs really well, but there may be a possibility that I could improve on that.

I would greatly appreciate your opinion.

Cheers

[BenR]

If you put carbs on then you will be deriving the ECU of sensor information from the MAP/MAF and the TPS. Without these informations the ECU cannot lookup the correct ignition advance reference on the ignition 3d map so you will be running with a set ignition timing i suspect.

It would be easy to test with a timing light and by revving the engine, just check if the advance stays the same.

This is very poor for engine performance, i would fix it.

To use the OE ecu you will need to hook up a vacuum manifold and run the MAP sensor off it, along with the brake servo (i hope your car is MAP not MAF).

You will also need to adapt the TPS sensor to the carb spindle and then reset the values to stock for idle and WOT.

[eight-six]

[quoute]If you put carbs on then you will be deriving the ECU of sensor information from the MAP/MAF and the TPS.
Without these informations the ECU cannot lookup the correct ignition advance reference on the ignition 3d map so you will be running with a set ignition timing i suspect.[/quote]

Pretty sure that’s how the system is currently configured. The TPS is just hanging loose, and almost certain the MAP sensor isn’t connected to anything.

Quote:It would be easy to test with a timing light and by revving the engine, just check if the advance stays the same.

Will see if I can borrow a timing light to check it out.

Quote:To use the OE ecu you will need to hook up a vacuum manifold and run the MAP sensor off it, along with the brake servo (i hope your car is MAP not MAF).

TPS

For the TPS signal I need to customise the spindle on the Carb so that as the Carbs open the spindle acts on the TPS and gives a throttle position reading? Is there any easy way of doing it or is down to how creative I can be? Do you have or know of any images which shows a TPS mated to a Carb spindle, just so I can get an idea in my head of how others have carried it out?

How would I go about resetting the values for idle and WOT, simple ECU reset or something more complex. I presume by you saying I need to reset the values – the ECU would read what the new TPS value of idle is and then when WOT it would register the TPS WOT value? After that its job done or is it more complex?

I suspect its best I do a test on the TPS first to check it is still functioning and sending a reading to the ECU? What’s the best way to do this?


MAP

The MAP sensor needs to register the inlet manifold vacuum? As the dual carb manifold essentially has 4 separate runners I presume I will need to tap 4 separate holes for each of the runners so I can then set a vacuum line up for the MAP? If this is correct I presume there is are issues having each runner connected by a vacuum line? Again do you have any images or know of any that shows how this has been done?

Again I suspect its best I do a test on the MAP first to check it is still functioning and sending a reading to the ECU? What’s the best way to do this?




With the TPS and MAP connected and the ECU receiving a signal then I presume the ECU will gain full control over the timing and I should see better performance as a result? I presume I would need to return the base timing back to what it is before doing all the above?


Forgetting about the stock ECU for a second what system would allow me to replace the stock ECU and wiring loom and still have full control over the timing with my dual carb set up?

Cheers

James

[jamiemirror]

Quote:Forgetting about the stock ECU for a second what system would allow me to replace the stock ECU and wiring loom and still have full control over the timing with my dual carb set up?

http://www.picasso.org/mjlj/

[firehawk]

This is a pretty good solution to replacing the ECU completely when using carbs;

http://www.picasso.org/mjlj/

It does require, in addition to the controller board, an EDIS-4 box, a 36-1 trigger wheel and a quad coil pack but also lets you get rid pretty much everything that's left over from the original EFI system, including the distributor (you'll need to make a blocking plate to the head). It also allows you to use either a MAP sensor or a TPS for looking up from a 2D table.

I'm actually very tempted to build one of these but I think I'll give my own system a try first just for the hell of it.

Edit; Haha, damn you Jamiemirror and your quick fingers!

[BenR]

eight six.

For the TPS setup you will have to get creative. If the bike carbs already have a TPS on it, remove it and check the spindle drive shape......you might have to machine an adaptor to fit the toyota TPS. Then you will have to fabricate a TPS claming/attatching method.....its best to clamp rather than bolt solid as it allows you to run alot more adjustment.

To setup the TPS you need to have your TPS on the throttle body, measure the resistance at fully closed, and the resistance at fully open. This is done by using a multimeter set ot ohms and bridge the 5v and signal wires. Just mvoe the throttle and you will see the resistance change. You MUST match the stock tps resistance settings for idle and WOT (wide open throttle) or the map will be wrong.

To run the MAP sensor you need to tap the top of the manifold runner behind the butterfly (to prevent fuel dropping into the vacuum lines). Then you need to feed all the lines to a vacuum manifold with one takeoff on one side for the TPS, and one takeoff on the other side for the brake servo.

courtesy of Ian bergins photobucket lol.....i sent him the bits for the vacuum manifold. You can see how the manifold is tapped and the vacuum manifold arranged.






To set the MAP you dont need to, it runs off atmo pressure differential so no calibration is needed.

And for standalone igntion system, try KMS....but you will need a crank trigger setup, TPS info (you can use the bikes one and just scale it), a coil and the ability to map.

[eight-six]

Thanks for the answers and images Ben, very helpful.

Sorting out a vacuum feed shouldn’t be a problem. I had envisaged making up a small vacuum plenum like how is pictured in the photo. Resolving the TPS issue is going to be more complex.

What is your view on the Megajolt system in the link above which used the EDIS system from a Ford? Seems that this system only requires a vacuum for a MAP sensor and runs of a crank trigger system. Looks like it could be a very clean minimal install for the money. I don’t know however if this set up operates well at high RPM – need to do some more reading.

Is there any advantage to using the stock ECU over this system? Obviously this Megajolt system has increased adjustability.

What other key functions on the car rely on the stock ECU?

Cheers

James

[BenR]

James

The TPS adaption will be tricky, but not difficult........it will be harder to get the machining sorted if you dont have a machinist i would have thought.

Regarding management.......IF you can get your OE setup running the ignition, i think it will work quite well as it will be a 3d map and it will be mapped specifically for a 4age.

I dont know the megajolt system, but i am not a fan of cheap management solutions.......they become time consuming and a pain in the ass.