Tu9 - Tuning!?!?!

[Guest rallymini]

I've found a couple of threads relating to tuning the diminutive 954 engine and the concensus seems to be go bigger, you'll get a lot more power for your pounds. However, I am considering using the engine as a basis for a S1000 rally car so have no choice but to stay with the engine size....

 

I have a complete engine from a 1995 AX with fairly low mileage. I have also got a late VTR head which seems to have the biggest TU valves. It looks like it might just fit, but there is fag paper clearance between the valves and liners, but how much clearance do I need? Plan B is to use an AX GT head which has slightly smaller valves.

 

The VTR head has roller rockers which have been described as not being very good, but if you look at tuning a Pinto or A series engine Vizard rates them for use with high lift / high spring rates as they reduce the side load on the valve. Am I missing a down side with the VTR rockers, somebody suggested the springs are softer so the engines to do not rev so high before valve bounce sets in?

 

The 954 engines have been used by the F1000 competitors quite successfully, regularly reving until valve bounce sets in at around 7,500 - 8000RPM (apparently). To make good power, the engine will need to be regularly reving to 8000 and possibly beyond - experience anybody?

 

Looking at cam suppliers, CAT cams seem to be quite accomodating with a wide range of standard and custom profiles. Does anybody know if they've done any 954 high performance cams?

 

On the induction side, bike carbs seem to be increasingly popular and highly rated so they seem like a good choice.

 

Any advice welcome...apart from putting a bigger engine in!!!

[Rippthrough 98]

Sounds like youve already done the legwork tbh!

Regarding the valve clearence - I don't think the gap would cause any trouble, but it might have a major valve shrouding effect that could possibly make the TU3S head a better bet, although someone here has compared both and reckoned the 1.6 head had better ports.

Certainly my TU3S head is needing a fair amount of reworking.

 

The roller rockers are fairly heavy and the springs are softer, less cam choice too, I'm sure there was something else too but I'll be buggered if I can remember!

 

You can lighten the original solid rockers by a fair amount, the easy way of which is to replace the bolts and nuts at the end of the arms with shorter, lightweight bolts and lightweight, half-height locknuts.

[Sandy 189]

I would also lean towards the TU3S head, the smaller combustion chamber means it won't need such severe skimming to get the CR up and the valve sizes on the later heads are arguably too big for your purposes and will be largely shrouded anyway. The TU3S head is perfectly capable of exceeding 100bhp with minor work, which could be your realistic target. The 954 has smaller big end size than the other TU engines, so you can't mix and match rods, unless another engine type yeilds a useful size.

 

With the TU3S head i'd suggest the 4901101, any wilder than that might well make it impossibly peaky, bearing in mind you're going to be limited on the ratio options with the MA unless you add £1100 to your budget for a Quaife gearkit!

[Guest rallymini]

Thanks for the advice, Vizard shows a lot of concern about shrouding on the A series head, particularly the section between the valves. I initially thought shrouding by the liners was unimportant but it's becoming clearer that all flow is important as the gases need to get in and out of the combustion chamber as well flowing throw it.

 

I welcome the cam advice - I was thinking of something a bit more wild, but was concerned about it being very peaky, not a good idea in a rally car. Have you seen this cam used in a 954 engine?

 

Gearbox wise, I have an MG ZR box with a LSD and a standard 4.2 diff but can go up to 5.1 dependent on how high it will be reving. I've already got the box in another rally car and was contemplating swapping the internals into the Peugeot case, but haven't started looking at Peugeot/Citroen ratios to see if they offer a suitable alternative - any suggestions? The regs allow a dog box, but that really is stretching the budget!!

 

Next decision is which car to fit it into? The Metro rally car, good handling but slightly heavy (diesel TU engine was used by Rover so should be a fairly easy conversion) or the Mini rally car, excellent handling, very light and excellent fun! or buy yet another car, probably a 205 or 106 which I would expect to have even better handling and light weight... my 205 GTi may get a new life

[Sandy 189]

I'd be inclined to go with the 205, it's easy to make it handle well with the alloy TU, it's light enough and it's always going to look better than a Metro IMO. Vanity may not be a priority, but it might just keep your faith intact on darker days!

 

I haven't seen a tuned 954 yet, I was simply projecting downwards what i've found with the 1124 and 1360 TU's.

 

The gearbox issue is an interesting one, the ZR box you have is definately the MA based one and not the VVC? There are a couple models in the Peugeot range with a 4.9 FDR, the only one I know of is some S2 1.0 106's. Otherwise, 4.54 is quite popular. The main problem i'm alluding to though, is the 1st to 2nd gear drop, which is unavoidable, because the tallest OE first you can get is 3.417 and shortest second 1.95, so that gap is always going to need a fairly broad spread of power to avoid dropping into a hole off the line.

[Rippthrough 98]

The gearbox issue is an interesting one, the ZR box you have is definately the MA based one and not the VVC? There are a couple models in the Peugeot range with a 4.9 FDR, the only one I know of is some S2 1.0 106's. Otherwise, 4.54 is quite popular. The main problem i'm alluding to though, is the 1st to 2nd gear drop, which is unavoidable, because the tallest OE first you can get is 3.417 and shortest second 1.95, so that gap is always going to need a fairly broad spread of power to avoid dropping into a hole off the line.

 

 

This is the biggest problem, even with the 1360 the 1st to second gear gap is a yawning hole, the increased rev. limit may help you here though, even if you go for a punchy midrange cam and engine spec you might want to rev it furthur out in 1st than you normally would.

 

If you are going bike carb I would definetly be looking into a 3d ignition sytem to go alongside it.

Edited January 3, 2007 by Rippthrough

[Guest rallymini]

Interesting that the ZR box has the same 1st and 2nd gear ratios you mentioned - 3.417 & 1.947. Reving to 8Krpm drops the revs to about 4.5Krpm, which is probably tolerable.

 

Which Peugeot has the 4.9 diff, that sounds like a more cost effective than the special 5.1 diff?

 

The engine spec includes the budget Megajolt 3D ignition system. Not a professional system but it seems to be getting a lot of use without reports of any reliability problems.

 

The 205 is definitely an option and I know they are an excellent chassis, but their 'achillies heel' seems to be the rear suspension travel. Reading the 205 rally forum, it seems to be quite a concern and the cause of several incidents. Having said that, I know the Metro also suffers from problems, so the 205 may be the lesser of the evils, particularly in the forest.

[Guest rallymini]

.... Forgot to ask, which Peugeot is fitted with those gearbox ratios?

[Rippthrough 98]

The engine spec includes the budget Megajolt 3D ignition system. Not a professional system but it seems to be getting a lot of use without reports of any reliability problems.

 

 

Just installed on on a VW engined rally machine - it's great - in fact it's better than most proffesional systems these days.

[Sandy 189]

Might be worth seeing if you can use these:

http://cgi.ebay.co.uk/mini-1275-pistons-co...1QQcmdZViewItem

 

As mentioned above, the series 2 106 1.0 in some cases had 4.9 FDR.

[Guest rallymini]

Great minds think alike!!

 

I've got an old set of 1275 pistons that I measured and confirmed they are the same diameter as the 954 engine pistons. I did some searching on the net to get some dimensions for the 954 pistons to see how similar they are but there was insufficient info to know for certain. So the plan is to get the engine out of the car, strip it and then do a comparison.

 

The other option I looked at was using motorbike pistons, there are a couple that have the same diameter, but it looks like the pin to crown height are way off. Again, I want to get the engine stripped to double check.

 

I don't suppose you know whether the pistons will fit....?

 

Thanks for the advice on the gearbox, i'll keep an eye out as it releases some of the budget for the engine

 

Thanks also, Rippthrough, for the good feedback on the ignition system.

[Rippthrough 98]

Thanks also, Rippthrough, for the good feedback on the ignition system.

 

 

The more the merrier!

 

I used half hieght aluminium locknuts and hollow versions of the standard bolts on the adjuster for the rockers, I think they alone saved about 8g per rocker, and it's right on the end of the rocker where it matters the most too. Then shaved another 12g off the rocker arms themselves.

Cost about £8 for the nuts + bolts from local specialist so well worth the saving imo. Of course you could go nuts and get titanium version but it'd probably run to about £50.

[Sandy 189]

The code for the 4.9 box is CD39.

 

I'd be wary of most bike pistons, they aren't usually designed for as much thrust angle.

Edited January 5, 2007 by sandy309

[Rippthrough 98]

Slight divergence.

 

If anyone wants some ally nuts and can't get hold of 'em then my local stockist has them in at £5 for the set of eight - anodised in various colours - full height rather than half height like mine though, can't see it being much to post a set out, probably a pair of 1st class stamps and an envelope.

Edited January 5, 2007 by Rippthrough

[Rippthrough 98]

Just found somewhere that will do me the titanium half nuts for £12, bargain!

[bren_1.3 1]

whats the big advantage? im slightly lost... lighter valve train?

[Rippthrough 98]

whats the big advantage? im slightly lost... lighter valve train?

 

Yep, same as when using lightweight valves etc, less stress and less mass to move.

[bren_1.3 1]

am interested. PM sent.