Audi Throttle Body Fitted - Loss of Performance??

Only my second post so please bear with me.

Just had a 2.2 Audi Quattro throttle body fitted to my 1983 1.8 GTi as part of an ongoing exercise to rid the engine of air leaks, improve idle and generally tweak up the performance along the way. Had the inlet manifold machined to match etc etc. The Audi WUR has not been sourced yet.

Although it's running sweet it appears to have lost a bit of power and isn't as responsive pulling away and also in the higher gears.

I know, well I've read, the Audi WUR needs to be fitted to fully realise the power gains but would not doing this cause a loss in performance?

The lad who has done it for me works in an MOT testing station and has set the car up to run a bit richer than required. Would the CO2, hydrocarbons and lambda settings have to be adjusted/reset for the Audi throttle body?

Anything constructive would be greatly appreciated.

Cheers

Paul

You should never do the throttle body without the WUR.

The first butterflies are the same size but the second one is quite a bit larger. So when you bang the throttle open the engine tries to take in more air but will experience a lean period. This is why the Audi WUR has a vacuum connection, it detects the loss of vacuum pressure and momentarily lowers the control pressure which in turn causes the mixture to richen until the negative vacuum pressure returns. Overall effect is that the throttle response is better otherwise you might notice a flat spot.

To be honest the throttle body / WUR change will not get you any more power unless you get the WUR control pressures adjusted. Commonly known as the WUR mod, it involves drilling a whole in the back of the WUR on the brass dome, which reveals an Allen headed screw, you can use this to tweak the control pressure and hence the mixture. Often kjet runs lean higher up the revs, this will allow you to correct that, a better mixture with perhaps a little more advance could see a few bhp back.

Cheers Ade,

It was only done as there was a leak on the original throttle body and I thought while it's off why not put an Audi one on. Otherwise I would've kept the effing thing standard. Now it ticks over perfectly but, as you described, has a flat spot on take off and generally isn't as responsive.

Should have a 2.2 WUR sorted this weekend. Is the mod tricky and is it a case of trial and error with the mixture setting?

Cheers
Paul

The mod is simple as long as you have a pressure gauge to hand.

It would also be useful to have a CO meter as well to set the CO once the pressure is set. Although to be absolutely sure a rolling road session would assure you that it is not running lean anywhere through the rev range and possibly allow the operator to add a little more advance to give maximum power without causing pinking. Having said that you are at the mercy of the advance curve of your dissy / vacuum advance, but it would confirm they are still advancing well.

Thanks very much Ade

well at least i found this out now,what car do i need to get this?just building up my 2.0 8v and was planning on putting the lrg audi throttle body on it ?

Right…

Audi wur is on, vac pipe connected but the mod has been shelved for the time being.

The lad who fitted it had to adjust set up at the throttle body as it was ticking over at 1600-1700rpm fully warmed up. Left his place with it at around 800.

Started it up from cold this morning and after 30 seconds of a bit of searching, it sat firmly ticking over at 2000 rpm.

Are set up adjustments best done during warm up or is there still something I'm missing?

Could I still have an air leak somewhere?

Did you measure the system pressure and cold and hot control pressures ?

Not sure Ade. I'll have a chat with him later.

What kind of readings should we be looking for?

Cheers

I am way at the moment so I don't have my reference book with me. I am sure it has been discussed on here before though, do a search for control pressure.

It s the only way you can set he WUR up, it is a pressure control device.

Been away myself Ade. I've had a read of your older posts on this matter and I think the best thing to do would be to drop it off at Awesome (only 2 mins away) and let the lads there set it up.

I spoke to them and it's something they can sort, albeit at £70 an hour.

One thing that struck a note is you mentioning the possibility of the engine running too hot if the control pressures aren't set up. Warm weather aside, it's been warming up quicker than usual. Cold starts are harder as it used to start on half a turn. Warm starts have been a nightmare - yesterday it wouldn't sit and idle, it kept cutting out leaving me to feather the throttle. When it came to having to put it in reverse I just wanted to kick it in. Very very frustrating.

At this moment in time I feel like putting it back to standard.

Should I persevere? I feel like I'm further behind now than when I originally started, which was only a quest to get rid of any air leaks.

Cheers

Paul

Hi Paul,

Well going back to standard should get her running properly again. But the larger throttle body and WUR will give you a better throttle response and maybe a little more power higher up the rev range as the original setup does tend to run lean, the adjustable WUR allows you to correct this and gives you a fuel squirt when the throttle is banged open quickly.

It is no surprise it is running badly, I bet the control pressures are all over the place cold and hot. The control pressure determines how much fuel gets injected for a given amount of air flow, you may be too lean or rich for both cold and warm running !!

Awesome should be able to sort that out for you inside an hour, try and negotiate a fix price to set the WUR up. They will need it over night to be able to set the cold control pressure.

Alternatively find someone with a kjet pressure gauge and set it up yourself. You will need a gas analyser to set the CO once you have the control pressure sorted.

Good luck