16v WUR onto 8v

looking at various threads this seems to be a good idea, but adjustability aside, can anyone tell me whether it'll give me a significant improvement over the original WUR and why? what's wrong with the 8v unit?

i've tested the 8v item fitted to the engine, it's functioning perfectly. i've got a tested 16v unit waiting to go on tomorrow, it'll be interesting to see if there's any difference.

 

i'm planning to connect that to the old breather connector on the manifold. i stripped it down to have a look at how it worked. manifold vacuum holds the control pressure down, sharp throttle opening causes an increase in manifold pressure which briefly richens the mixture.

i was thinking that on a sudden throttle opening, the air rushes into the engine faster than the airflap can respond, so a little extra fuel squirted in is a bonus. a bit like the acceleration pump on a carburettor.

is there a problem with the mixture running lean briefly under acceleration on the 8v though, or is it more of a 16v problem, what with it being freer breathing an' all?

 

think its more for modded cars ?

the 16v can be ajusted for more fuel if you rolling road it and find its weak somewhere

 

You'll struggle to get a vac connection to fit as the oil filter/cooler is very close to the the right of WUR on the 8v, the only way you'll get a vac hose on is if you mount the WUR upside down. I didn't bother to connect mine up.

I set my pressure using a borrowed pressure gauge & it has improved response lower down the rev range but it does go a bit flat after 4500rpm, I suspect that having the pressure properly set up on a rolling road may rectify this.

 

Waste of time on a standard car I'd have thought, as they fuel pretty well anyway. I've got one on my track car - 2.0 8v with a pack d head and 285 cam - and it helped a lot, although it's still too lean at the top end.

I ran a vac connection to a T piece in the pipes around the inlet manifold.

 

righto, cheers guys. engine is a 2l 8v with mr shed p&p'd standard valve head & kent gs2 cam, so this might well be a useful thing to do as the breathing has been improved over stock?

i've got the pressure testing kit to set the control pressure once it's fitted and running, i'll fit the 16v WUR upside down and plumb in the vac connection too. once i've fitted the new downpipe that's sat in the shed i'll have somewhere to stick the wideband o2 sensor that's on its way, then i can see what's really going on with the AFR, but until then a trip to the local bosch specialist to set the idle co will have to do.

engine's probably kicking out about the same bhp as a standard kr, so do i need to set the control pressure to the same spec as a kr (as a starting point) do you think?

 

I have done this mod to 1.8 8v solid lifter, cars runs slightly better.

 

Sounds worth a try then, on that spec. Ideally you want to set it up with the o2 sensor. You can always stick it in the end of the exhaust as a temp measure. You could start at the same control pressure, or a smidge lower, but it's pretty hit and miss if you don't measure the exhaust output.

Was the car properly set up on the old WUR, or just left as standard? I think you can adjust the 8v WUR by the little plunger in the front of the unit. Only goes one way though - you have to strip the WUR down to bring it back out.

 

unfortunately no, the fuelling's all still set as standard, but the idle co is at 2.5 - 3%, a little high perhaps. system pressure is 5.4 bar, control pressure when warm is 3.8 bar.

i'm going to take the plunge and buy an innovate lc1 with gauge tonight, so that should be with me by next week. that way i can get the fuelling within the ball park by clamping it in the tailpipe and going for a drive. i gather i'm aiming to keep the airflow meter operating over the same range in the cone as before, so i should be providing extra fuelling by increasing system and control pressure in proportion with each other.

it would be interesting to see if there is any leaning off on accel which the 16v WUR would counteract, would i be able to check this with the afr gauge?

 

I'd be surprised if it isn't running a bit lean, currently, given the spec and the setup. An AFR gauge should help, however, I don't think they're supposed to be just chucked down the exhaust pipe. The Innovate clamp just holds the tip of the probe into the exhaust flow. I'm not sure how accurate a reading you'll get if it's held differently. Worth a try though.

For comparison purposes, my standard 1800 Kjet Rocco read about 15:1 on part throttle, 18:1 on tickover, 20+:1 on the overrun, and about 13:1 on WOT Acceleration, leaning off a bit at the top end.

 

as far as running lean through the rev range, i have no idea. while i was driving it over here it was pinking slightly on the transition from closed to part throttle, which i put down to wear in the vac advance causing the timing to advance too far, too quickly. ended up changing the plugs from mk3 to mk2 items and it's been fine ever since. the mk3 plugs looked very white, but the top of the pistons looked sooty. i think they were just too hot a plug for the engine. i've since had the idle mixture turned down from 9% (yikes) to 3% which is still a little high. no idea what it's doing at the top end, but i've not heard any pinking up there.

so your scirocco is pretty much right as far as AFR goes? i think i should be aiming for yes around 13:1 for WOT, 15:1 for part throttle/cruising, overrun i'm wiring in a cutoff solenoid. 16v WUR will be giving me acceleration enrichment.

i fancied getting the innovate exhaust clamp, but at 75 quid i'd rather make my own. it's necessary to feed the o2 sensor with nothing but exhaust gas on the sensor tip, while still allowing pure air to the back of the sensor. the probe has to poke up the pipe far enough to avoid the region where air is sucking back up due to the pressure waves in the exhaust.

 

This thread inspired me to finally conect up the vac hose to my WUR, as stated earlier it does have to be mounted upside down due to the oil filter/cooler being in the way.

I was only able to get one of the bolts on as the WUR is at a slight angle again due to the oil filter, I simply cut into the large vac hose that runs from behind the throttle body, put a T connector in and ran another hose to the WUR, there is a large coolant hose in the way but I just routed the vac hose behind it.

I cant say that it has made a massive improvement to the performance but it does "feel" as though it is pulling stronger from 3.5k up.

I'd say worth doing considering it only cost 6 for the vac hose & T connector bearing in mind that I don't have a CO meter or pressure gauge to set it up properly

 

don't know if you seen this before: http://www.scribd.com/doc/3299223/Bosch-KJetronic-Fuel-Injection-Manual-, it's available as a pdf somewhere but i can't find it at the moment. as far as i can tell when the WUR vacuum's plumbed in correctly, the less the manifold vacuum, the lower the control pressure, hence a richer mixture. so at wide open throttle manifold pressure is close to atmospheric so it's letting more fuel in?

do you think you're feeling better power at the top end because it was lean up there before?

 

I'm assuming that is what's causing the percieved improvement.

To be fair the control & sytem pressures may have been & may still be not set correctly, I did them myself with a slightly leaky pressure gauge. At the MOT the CO was 0.30% but this was rectified before the retest when it was 1.9%.

TBH I'm not obsessive, or rich, enough to get it properly set up on a rolling road.

 

around my way there is a company called TUNE-UP they come out to you and tune the car but its mainly set up for economy but atleast it will not be running rich or lean