From: Mikeymikemcmike (Original Message) Sent: 02/03/2008 13:08
Hi,
I have read in various places that it's possible to get a replacement pulley for the Volumex blower with less teeth and so get a higher boost. Has anyone done this and where might I be able to obtain a pulley?
Thanks,
Mike
From: hutch6610 Sent: 10/03/2008 00:34
Yeees lets try posting again shall we!
Have to admit that's a real pristine VX you have mikeymikemcmike - stumbled across it accidentally trying to create some more attachment space.
Did not know so many people would be interested in "overboosting" a Volumex.
It is possible to run at 1.6:1(reliably) whether using an 18 tooth pulley or messing around with the other sprockets / pulleys - its just easier to change the one on the blower, so if the car does not like it you can easily convert back.
Carburettor / fuel system must be in good order or it will give nothing but trouble - will pop back to buggery and break the blower belt.
Had this with a coupe a few years ago where the breather to the scavenge pump had been blocked off with a bolt.
It just would not run the way it should have without it blocked off - suffice to say i looked like a right w**ker and took the pulley off (never heard from him again)
I currently run a VX HPE with this blower ratio.
It has a standard fuel system, but equipped with Digiplex - although i have retained the stock distributor/ignition with a modified vacuum advance so that i can adjust it to get the right amount of advance i need.
Digiplex has been playing around recently, probably due to a dodgy sensor.
When starting from cold the engine will lock up at TDC as if "over advanced" put on the stock ignition wiring and it starts first go - so i know its a sensor fault.
If i then re-connect the Digiplex it will run all day without a problem, it's just a cold start problem.
The blower is modified with an oil tank on the rear of blower because my bearing man told me it could handle an extra 1000rpm if they ran in oil as opposed to grease.
When i re-built the engine around 8 years ago i substituted an IE engine with 40,000 genuine miles and put on all the donors "VX" parts, ported the head (cautiously) and baffled the sump for good measure - i can hurl the car into long right hand bends without loosing oil pressure.
The oil pump is also shimmed to give a little extra pressure, 30psi hot at idle, jumping to about 60psi at 2000rpm then up to around 85 - 90 max depending what oil i use (HPX gives higher pressure readings)
The only mistake i made was using Croma turbo IE pistons so i know my CR is well below 7.5:1 but they were all i could get back then - only got a PC three years ago.
The engine red lines in all gears with ease including 5th, would love to get another 1000 rpm.
A custom exhaust would also improve matters i am sure
Some standard VX's will only manage 5000rpm and Barry Waterhouse was impressed my car could "you have a very good one" and he was not being sarcastic!
I too had thought about using a Weber type "twin" injector fuel system to replace the standard set up but i could not justify the money i was quoted (call me tight!) and also it would still "wet" the inlet manifold.
Would love to see and drive a Guy Croft 45 conversion just to see how it goes.
The pulley you both mention with 21 teeth would produce very little extra power you could feel.
You can drill and tap the manifold to get a pressure reading but would be disappointed i am sure, my boosted VX shows only about 3 psi because the engine is drawing the boost as it is being generated - blank the manifold off and i am sure you would get around 10 to 11 psi although the engine would not run - remember its a "positive displacement blower".
I decided to go for a multi-point fuel injection system because i wanted each cylinder to get its own fair share of fuel and my theory is that i could cut off the water supply to the manifold so that it would cool the inlet charge although i intend to use water injection to help keep this in check and there are also other benefits i have been reliably informed by a friend with a turbo charged bike.
I agree 1000% with raparici that some sort of mapped ignition system is required hence why i used a Microplex and fuel system from a Croma Turbo IE.
Not perfect but at least i can test my idea.
I will later invest in a Mega squirt and dial everything in properly to the best of my ability.
The engine in the photos has standard boost but has the Croma system / ignition system grafted on.
Initial runs have been very encouraging - smooth idle, first time starting hot or cold (to be honest my carb HPE does anyway) and best of all revs up instantly, shame the airflow meter masks the super charger "wail".
If i run my coupe (stock carb) with a measured 1 gallon in an auxiliary fuel tank it will "slurp" down pretty much most of the fuel from cold in 20 minutes.
The injected engine uses a little less than half that amount again from cold.
The only way to test it properly would be to put it all into a car and road test it - hopefully soon.
Anyway hope i haven't bored you all into a coma with all this!
VX Injection manifold.jpg VX injection blower close up.jpg VX injection.jpg
From: pope_vx Sent: 11/03/2008 23:06
Hutch, congrats you've done a whole load of good work there and avoided most of the high costs that put me off trying something myself. In addition your multipoint setup is much better than the simple single point one that I had envisaged. I now know where to come to get some pointers on sorting out a few issues I have with my VX .
Chris
From: pope_vx Sent: 11/03/2008 23:14
Sorry, could you explain that bit about measuring the boost again please? I didn't quite understand what you're getting at. I'm pretty sure that I'm just taking a pressure reading off the manifold and it seems to work. I get a vacuum reading at idle but about 0.5 bar at wide open throttle under load.
From: hutch6610 Sent: 16/03/2008 22:34
Hello pope_vx
You actually get a reading from your boost gauge?
0.5 a bar sounds pretty good for standard.
My VX has a nipple which is tapped into the manifold next to the pop off valve and when i fitted a gauge got pretty much sod all!
About 3psi would you believe and with TWO different guages!
Like you said a "negative" reading at idle and only 3psi at full throttle - can't believe my blower is knackered.
Two duff gauges.........hmmm anythings possible.
Your experience has given me a kick up the backside to try the boost gauge again - this time will buy a brand new item.
I must also check my spilling bicause i keyp mayking mistax!
From: pope_vx Sent: 21/03/2008 00:05
Yes, I most certainly get a reading. Mine isn't quite standard, GC did some head work on it ages ago and it's got a DCNF conversion along with the 21 tooth pulley. It used to go like a rocket but after being laid up for about 6-7 years it just doesn't have the grunt it once had.
Can't believe your blower is only producing 3 psi from your description of the way yours runs.
If it isn't completely freezing and chucking it down this week-end, I'll try and get some photos of the installation and the gauge. As I recall, the gauge wasn't too expensive and the colour scheme looks OEM.
From: hutch6610 Sent: 21/03/2008 22:24
I Look forward to seeing your photos.
What did Guy do to your car if i may ask.
The DCNF is obvious.
Seems odd you should loose performance just because it has been laid up - take a compression reading, may help you pinpoint the problem.
From: pope_vx Sent: 23/03/2008 10:35
This may sound really stupid but to be honest I cannot remember everything that was done now . My only excuse is that all the work was done in 1995 and my life has move on a lot since then.
Mostly porting to improve flow through the head, different valve seats to allow it to run on unleaded, baffled sump, the DCNF, in-head stat (since removed) and removal of all the plumbing associated with the original carb setup. That's all I can remember now. It went really well although it was only producing about 160 bhp with about 160 lbft of torque.
It's probably only done about 10,000 miles since then. Compression is 160 psi across all 4 cylinders. It's now producing 135 bhp and 150 lbft. Any other ideas?
From: hutch6610 Sent: 23/03/2008 23:18
160 bhp with 160lb of torque - 25 bhp sounds pretty good to me and will make all the difference when compared with a standard VX, like "chalk and cheese" i bet.
160 psi is not bad - could be a little better but plenty good enough.
I take it you have rolling roaded it to come up with the new power figures.
Does the engine warm up to full temperature - no stat results in heat lost = power lost, but i doubt you loose 25 break.
Has anything been done to the car during or since the lay up?
What did Guy do with the exhaust - left it standard or is it modified - back pressure is the biggest killer of power on a VX and i agree with him.
Reason i ask is if you had the exhaust partially or completely replaced with "lets face it" a "pattern" item chances are thats whats killed your performance.
Guy recommends - if i remember correctly - a 36" equal length big bore tubular manifold (somebody had a photo of this fitted to a black VX coupe on this site!) and big bore all the way through with high flow silencers.
I had the same experience as you with my Alfasud - before putting into storage ran fantastic - when recommissioned i fitted a new Timax pattern exhaust and it just went "lame"
After much head scratching i noticed it did not even sound like a sud, so took off the back box and guess what? performance returned!
Also check if your vacuum advance is still working, remove the pipe from the carb and suck on the pipe.
They are known for perforating and you won't get full advance.
The Fiat Uno one is similar but has a lighter spring but this makes little difference.
Try Redex! believe it or not i have had good results with this stuff.
pour it down the plug holes and let it soak into the valves and seats - just follow the instructions - and when the smoke clears it may help.
From: pope_vx Sent: 24/03/2008 11:52
Cheers Hutch. Several bits of very good stuff there.
You've reminded me, GC also changed the inlet cam to one from a Beta IE to improve the top end. As for things done to the car since the lay up, lots of stuff but nothing to the engine except for the 21 tooth pulley and the boost gauge. When I got it back on the road I did have several issues initially (mixture too rich, 2 spark leads round the wrong way, running on 3 cylinders, timing out). These have all been sorted now and I have no reason to believe that any damage has been done as a result. Last year I also spent some time checking the valve clearances. In general, they seemed a little too tight so got some new shims and adjusted away to get everything as close to the recommended settings as possible. It made bugger all difference to the way the car ran. A few months later after the rolling road test (see below) I put them back the way they were on the basis that the car was running with them like that before and the extra 0.1 mm of lift might help.
The exhaust was left alone BUT the original back box rotted while the car was sitting and I replaced it with one from another car. Indeed, now you mention it, the engine does feel a bit restricted and unwilling to rev like before. Maybe a CSC tubular manifold and custom exhaust will help. Is there ever an end to the spending with these cars?
Sorry didn't explain the stat situation very well. I lived overseas for a few years and my car was set up accordingly: no interior heater, just cold air intake, no carb hot plate and the in-head stat. Since returning to the UK it's been a different story. So the interior heater is back in, in-head stat has gone but has been replaced with an external 3-way stat similar to the original, hot air intake has had to go back on (which restricts the inlet airflow ) and I'm going to reconnect the carb hotplate but with a 40C thermostat from the USA. Now the engine does get into the normal range but I still get carb freezing issues if the ambient temperature is below about 10C. I hope the hotplate should take care of that.
Yes, I had it on a rolling road last year to try and sort out jetting issues with the carb. Everything was tested with the engine properly warmed up. They found that one of the idle adjusters was broken which wasn't helping. I've since had the carb cleaned and got new adjusters. Not been back on the rolling road yet.
Vacuum advance is still working OK, ignition timing is OK and valve timing is also OK.
While it was off the road, I'd squirted some oil in the cylinders and turned it over by hand once or twice with the plugs out. Turned over very easily, felt smooth with little resistance. I've wondered once or twice whether the valve stem seals had hardened a bit but other than that I have no reason to believe that there is anything wrong internally and cannot see any benefits from going to the trouble of removing the head to have a look. Seems like your exhaust theory is the best bet at the moment.
Still trying to arrange a photo shoot for you but the weather has not been kind. Will see what I can do with the camera flash in the dark garage.
From: pope_vx Sent: 24/03/2008 19:24
Had a go at the photos today but didn't manage to get anything decent under the bonnet. However, I can confirm that I just drilled and tapped into the manifold to the left of the point where the pressure relief valve sits. From there it's just rubber tubing back to the gauge in the car. Photo of gauge below.
From: hutch6610 Sent: 26/03/2008 00:23
Right got the full picture now.
You got the head treatment, DCNF, IE inlet cam and the head mounted thermostat (now put back to standard) and the sump is baffled for good measure - sounds good to me - you have pretty much the same spec as my car but with original compression ratio, almost standard boost and a superior carb.
You just don't loose 25bhp because you lay the car up.
Betas can run tighter tappet clearances than specified - .35mm inlet and .40mm exhaust although you loose a little torque but the engine becomes so much quieter - its a personal choice.
The timing on the valves is slightly advanced although they open earlier to let the mixture in they also let the useful expanding gasses out!
Ask : jazzygeoffSA (next message) nicely what he has done ( pretty sure he has the 4:1 exhaust manifold Guy recommends)
Forget the CSC manifold it's for a normally aspirated engine with the cross over pipes and although better than the standard VX setup is not worth the expense - best to invest the money in the 4:1 system.
Strangely enough i don't suffer from carb icing and i don't use an air filter - which i know is very very naughty but doing only 14 miles a week now i can just about get away with it for a short period.
Valve stem seals usually harden due to extreme age and or overheating - you have not had any.
So no point removing head to have a look.
Take your back box off and road test your car to see if some of your power returns - they make a hell of a racket though.
I am afraid when it comes to modifying cars its a bottomless pit!
From: pope_vx Sent: 26/03/2008 09:02
Thanks again. Bottomless pit sounds about right. Given the amount I've spent on this car over the years, I could have had a very tasty 944 but that's another story.
"You just don't loose 25bhp because you lay the car up" - I've said the same to myself countless times and so I focussed on the settings over and over again. The exhaust back box is the only other variable that I haven't investigated but I don't think I'll get back 25bhp from that alone.
I assume that the 4:1 downpipe that you mentioned would have to be custom fabricated rather than an off the shelf item?
