32/36 DGV running issues

[onecamohv]

Hi Folks,

Wonder can anyone with good experience playing with DGV's point me in the right direction.

My bro has a 1988 toyota starlet that he fitted a newer 1991 4EF 1.3l 16v engine in, running a 32.36 DGV.
The car idles fine, and runs well on WOT with the wideband AFR showing around 12.5 which is fine.

The issues like coming from very low speed part throttle transition to WOT there is a massive flat spot that would nearly throw you through the window. For example taking off to go round a roundabout you go to take off and there is a massive breakdown in power, engine will nearly die its so bad, and then take off like a bat out of hell.

Another strange issue that may be linked is the choke (manual) doesnt do anything. half choke when cold, makes no difference. full choke just smothers it and the car cuts out. the Choke doesnt raise the revs in any position.

Could he have a blocked AUX venturi? float level ?

any ideas gratefully received!

[mrmk2]

Check out my thread, got massive help from this forum, and Onyd helped loads. I have the similar problem, just waiting for spring an some warmer wether to continue.

[Graham]

sound like the choke needs some fast idle, most carbs have an adjustment which opens the throttle a bit when you pull the choke.

flat spot is is accel pump related, diaphragm split, jet blocked, non return valve blocked

whatever your faults are it wont be a blocked aux vent

[onecamohv]

sound like the choke needs some fast idle, most carbs have an adjustment which opens the throttle a bit when you pull the choke.

flat spot is is accel pump related, diaphragm split, jet blocked, non return valve blocked

whatever your faults are it wont be a blocked aux vent

Cheers Graham, Accel pump is definitely working sorry I should have said all the basics are checked.
Accel pump working perfectly, carb has just been rebuilt.
Healthy Accel squirt into the primary.

[Graham]

i did ask what cam was fitted, ive just re-read the first post, its a modern 16v engine, if he has grafted a carb on to a modern banana bunch intake manifold thats most likely the issue

[onecamohv]

the 16v engine in the car was originally carb from the factory. all we did was weld on a weber 'PCD' plate in place of the Aisin one orginially fitted. no air leaks, accel pump working, jetting should be there or there abouts, new dizzy cap etc, timing checked all ok. its like theres something not working between part throttle and wot. The transition is just a massive flat spot, and then off she goes

[Graham]

what happens if he feeds the power in SLOWLY?

its worth looking down the carb and seeing if fuel comes out both aux vents, i did have one carb where the internal tube in the aux had moved.

[onecamohv]

its better, but still there. you can nurse it and still feel it but it passes.
gets much better when hot. its not just a 'hesitation' feels like it totally ran out of fuel for a second then bang. are DGV's sensitive to float level? dont think that would cause this issue though would it?

[HonkyWhiteTrash]

One aux venturi installed incorrectly so that it's blocking the fuel path? Seem to think you can fit them the wrong way round. Perhaps on primary by the sound of it as it clears at bigger throttle opening positions? Might be worth working out if the problem occurs on primary side or when the secondary side is coming in.

[Graham]

what you need to know is if its going rich or lean when you boot it, if its going to either extreme it will bog, assuming 26/27 chokes then they are pretty big for a 1.3 it might be you need bigger mains to richen it up, then bigger airs to lean it out at the top

[onecamohv]

what you need to know is if its going rich or lean when you boot it, if its going to either extreme it will bog, assuming 26/27 chokes then they are pretty big for a 1.3 it might be you need bigger mains to richen it up, then bigger airs to lean it out at the top

totally lean, this is not a 'rich bog' this is a throw you towards the windscreen cough. we've a wideband afr hooked up and its near perfect 12.5:1 from the low speed bog to the redline, so the mains and airs i put in it seem spot on. the wideband jumps to max 25:1 afr for a second but thats just the guage taking a fit from whats going on.
i might try take a video next weekend as they say a picture or video paints a thousand words!
next step i think is whip the carb back off and strip it to make sure i havent done something stupid

[Graham]

i once had a similar problem when i fitted a twinchoke to a renault 5 engine, it wasn't as severe as you describe, but putting a bigger jet in the secondary idle fixed it.

a word of caution, a very rich mixture can flood a lambda sensor to the point it doesnt actually read and therefore shows very lean

[onecamohv]

Ok so did a bit of digging today, and here's what I found.

Whipped the carb off, and had a look.

Firstly , the float level was way too high, should be 41mm for brass floats, it was about 30mm.

Also found that the 4.5 aux Venturi was in the primary, and the 3.5 was in the secondary. What sort of effect would that have??

Rest of the settings found were as follows:

Idle jets : 45/45
Aux Venturi : 3.5/4.5
Mains : 125/130
E/T : F66 F66
A/C : 170/160
Pump jet: 45 squirts into BOTH chokes

Set the float height, and swapped the aux Venturis to the right chokes. Was too late to test. Should we see a difference?

Thanks guys!

[Graham]

dont think you will notice much if anything on the aux vents, pump jet shouldnt squirt into both barrels, you can get a pool of fuel build up behind the closed secondary, which is suddenly dumped in the engine when you do open the secondary

[onecamohv]

should i solder it up?

the problem is definitely related to the primary i think. any other ideas Graham?

[onecamohv]

so went on a drive last night and its pretty much the same.
Im going to try a 50 pump jet in primary only, and 50/55 idles.
any other recommendations anyone?
thanks for any help