1.3 tuning help

I've just had my driver's engine rebuilt, and a 5-speed box put in..

but I've noticed that the car just doesn't have the acceleration even when it was running on 3 cylinders,

I think this is to do with the mechanical advance on the 5-speed box, the car just doesn't have the power to pull through the gears,

Soooo…. I'm trying to figure some ways of getting more power to the car without being drastic, so no boring etc.

If it helps, I've got a 34ICH weber on it.

Thanks much

I'm not sure what you mean.

The mechanical advance is within the distributor and is a pair of centrifugal weights that advance the ignition when the revs rise. There is also a vacuum advance in the dizzy that stops it stalling when stopping quickly.

If the engine is set up properly, and the ignition timing is spot on, the only real way to get it to turn a bigger gear is to add torque. The only realistic way to add torque is to bore it out. :twisted:

Personally, I would rather sit at 70 on the motorway and save the hassle, although when the twin 40's I have get fitted, I may need the extra gear just to get between petrol stations :mrgreen:

Matt meant "mechanical advantage" - basically, each of the first four gears on the five speed box is higher than it was on the original four speed box - basically, the gearing is taller, which is affecting the acceleration

I'm certain the box is an 8P, but I'm wondering of there were different ratio boxes fitted to different Polos

Anyway, we have a VERY simple choice

1. Make more power so it can pull the higher gearing
2. Fit the four speed box back on

At the moment, I'm thinking that the ignition isn't quite right - when I pull the vacuum hose off the dizzy diaphragm (to set the timing) it makes no difference to the timing or the tickover speed - prior to the rebuild, the revs used to drop as soon as the hose was pulled off

Its possible that the diaphragm in the dizzy has been damaged then, which will also have the bonus prize of weakening the mixture (due to the inlet manifold's vacuum connection pulling a flow of more air in, rather than just statically pulling the diaphragm to alter the timing).

Stick a timing light on it and see if the vac connection on/off changes the ingition point.

NigelO said

I'm certain the box is an 8P, but I'm wondering of there were different ratio boxes fitted to different Polos

your right, the 8p is a common box on alot of polos, the polo gt however has a short ratio box. when i get the chance ill look at mine and get the code.

NigelO said

Matt meant "mechanical advantage" - basically, each of the first four gears on the five speed box is higher than it was on the original four speed box - basically, the gearing is taller, which is affecting the acceleration

I'm certain the box is an 8P, but I'm wondering of there were different ratio boxes fitted to different Polos

Anyway, we have a VERY simple choice

1. Make more power so it can pull the higher gearing
2. Fit the four speed box back on

At the moment, I'm thinking that the ignition isn't quite right - when I pull the vacuum hose off the dizzy diaphragm (to set the timing) it makes no difference to the timing or the tickover speed - prior to the rebuild, the revs used to drop as soon as the hose was pulled off

Unsure of the exact gear ratios but there might be another choice: split the transmission and transfer the final drive from one to another. This will only work if the gear ratios are the same/very similar but its the FD which is different. And it will cost about £150 in the specialist tools to take gearboxes apart and successfully get them back together, too….. so probably not worth the hassle.

advance the timeing 3. to 5 degrees and put a 1.6diesel caddy box in it loads of grunt then mate

bertmk1swallowtail said

advance the timeing 3. to 5 degrees and put a 1.6diesel caddy box in it grunt like fUUCKK then mate

Its a small block, the big block gearboxes won't fit. No Mk1 Golf 1.1 or 1.3 was ever sold with a 5 speed. Hence the need to seek out a Polo box and custom gearbox mount.

paul_c said

bertmk1swallowtail said

advance the timeing 3. to 5 degrees and put a 1.6diesel caddy box in it grunt like fUUCKK then mate

Its a small block, the big block gearboxes won't fit. No Mk1 Golf 1.1 or 1.3 was ever sold with a 5 speed. Hence the need to seek out a Polo box and custom gearbox mount.

or the mk2 golf small block has a 5 speed too, and needs no custom mount.

PaulC - pulling the vacuum tube off the dizzy makes no difference to the timing (although it used to, pre-rebuild)

I've checked the actuation of the dizzy - sucking on the pipe makes the dizzy baseplate move and it returns just fine too

I've also checked that the vacuum pipe is actually getting vacuum, which it is.

I'm confused - the engine really should feel much stronger - its got new rings AND the head was skimmed to increase the static CR

I am going to replace the vacuum hose, just in case there's a split that I haven't seen and I'm also going to try advancing the ignition a bit - I'm DETERMINED to get this thing running properly…