Xflow Performance

[New7er]

Just back from a blat round the lanes, 6000 rpm from the old donkey and I've never had it tuned or even balanced the carbs since I bought it 6 months ago - if it ain't broke don't fix it!

 

However, although it still impresses the passengers I feel it is not pulling as well as it could in 3rd, 4th and 5th. 2nd is a scream literally and the noise is incredible. Having had the pleasure of track driving a couple of 1.8k super lights recently (noise not so good) I could't help feel a little disappointed at the top end performance of my trusty xflow.

 

Can anyone enlighten me as to what I should be expecting from a 135BHP Super Sprint of 1990 vintage, top end rpm, 0 to 60, 30 to 50, 50 to 80 say? ..and how should it compare, if properly tuned, with a k series. They seem to rev like crazy with the power all at the high end just where the xfow appears to flatten out.

 

Before you know it upgraditis will have set in!!

 

Thoughts?

 

New7er

[Joe 90]

Too many variables ❗ (cam, exhaust, car weight, driver weight, gearing and so on). An eight valve XFlow will never have the free revving top end of a 16V engine, but IMHO mid range torque is more important. Sounds like upgraditis is in the incubation stage. My best advice is to ask yourself what you really want out of the car.

 

Oliver

 

98,000 miles so far

[oilyhands]

'mid range torque is more important'

 

A supersprint xflow makes peak torque at around 4500, a stock K series makes peak torque at around 2500 and sustains this to within 90-95% of peak till about 5300. What could be more mid-range than that?

 

Oily

[ashaughnessy]

How many miles has your xflow done? It could be quite tired by now. Also, that five speed box might not help matters, I reckon the four speed box is better suited.

"If it ain't broke don't fix it" - but it is broke, in a way, because you aren't happy with it. Check the valve clearances, ignition timing, carb balance, plugs, distributor, etc. - the basics. Perhaps get it fettled at a 7 specialist. Worth a try before you spend serious money.

 

Also, check the brakes, especially the handbrake. Do the wheels run freely? Are you getting any drag that is sapping engine power?

 

Anthony

[greg]

Is this a stock Caterham Supesprint? In which case in might well be tired and in need of some TLC. Also caterham were apparently quite optimistic about the output and 120BHP might be a more realistic figure.

 

That said, giving Roger K a few bob and he does quite a good (real) 155BHP.

 

That said there could be many other variables - the Exhaust may be naff.

 

On the grearing front a decent 4 speed is my prefered box, especially a beefed up box, with a very high first (2.04) that will allow silly speeds in 1st. This may result in strained cruising revs mind.

 

Upgradeitis is expense and most incurable, although budget holders can make it go benin for a short while, but its always there, waiting for the next upgrade opportunity.....

 

Greg, Q 86 NTM (Green 185BHP XF)

[New7er]

Yes, it is a stock Caterham built Super Sprint with no current upgrades and has done 35000 miles. Still holds good oil pressure, no leaks and has not been tracked - so they told me! Its got a side exit 4:1 Comp exhaust and discs all round, all free moving.

 

I think an intial tune at a specialist is on the cards and see what differnce that makes. R. King next maybe!! Whats the cost of a 155bhp upgrade likely to be?

 

Thanks for the advice guys

 

New7er

[greg]

Roger is the best person to ask about costs, and he will only give guide figures as it depends on what he finds.

 

Does the engine breath heavily (lots of air/oil vapour coming out of the breather pipe)? These engine suffer from naff pistons (the used the 1300 pistons that were not designed for this power, Forged ones are much, much better) which ends up breathing heavily and sapping power.

 

Taking a car on a track is not all the horror people crack it up to be. Yes the car gets cained, but owners who track cars usually look after them allot better.

 

Greg, Q 86 NTM (Green 185BHP XF)

[SteveP]

New7er,

 

I know exactly what you mean. When I first drove my Supersprint (also around the 35000 miles mark) I thought it was quick, well it is quick in 1st and 2nd.

 

A rolling road session confirmed that it was producing 135bhp at the flywheel (estimated), but only around 100 at the wheels, which I found a little worrying - spec is 244 cam, 45 DCOEs, 4:1 exhaust, steel rocker assembly but standard pistons.

 

Then I was a little surprised that my 'runaround' Golf GTI 1.8T can easily keep up with it once you get into 3rd and on - to be honest, the Golf feels quicker. The 7 certainly doesn't leave it for dead.

 

Having now convinced myself that not all of the power is going down properly and the continuing the quest for the 'christ, now that really is quick' type performance, it's going in for an rebuild to the fabled 155 RK spec

 

Additions such as the 3D mapping and a better silencer should improve things no end I hope.

 

Oh, and the 15" wheels are going in favour for 13" on stickier rubber - should improve things a lot.

 

Peak power is at 6500, torque at 5100, 0 - 60 I guess is about 5.5s, not sure on the others.

 

SteveP

 

Edited by - SteveP on 28 Aug 2002 13:03:23

[New7er]

Thanks Steve,

 

Glad to know I am not alone and it was just me! I have 14in KN wheels and have thought about the 13in variants. Let me know how you get on with the rebuild and what the difference is like. I was surpirsed about the comments on ethe 4 speed box as a number of others with that box have suggested to me they wished they had the 5 speed. Grass on the otherside perhaps although and I can see the logic with the 4 speed and getting a better spread of ratios more suited to the car.

 

 

 

New7er

[greg]

SteveP,

 

I think that once you are in 3rd you are doing a fair speed, and hence the airdynamic brick like qualities of a 7 will restict it. I agree that a 3D systems are an excellent improvment, and lighter (13") wheels also help.

 

Let us know what you think of the RK155!

 

Greg, Q 86 NTM (Green 185BHP XF)

[ashaughnessy]

If you get a rebuild to exactly standard specification, budget at least £2000, that's assuming you take the engine out and put it back in yourself. For a modest upgrade budget at least £3000. It may cost more than this, but probably not less. 35,000 miles means your engine is probably ripe for a rebuild. I imagine it breathes quite heavily from the crankcase breather?

 

My tired old bog standard 4 speed live axle supersprint accelerated well up to about 85 or 90 mph (as indicated on the speedo), but didn't accelerate much beyond that and only managed to get to 100 mph (again, according to the speedo) on the longest straights. I can't imagine much keeping up with it in 3rd gear or lower but once in fourth it never felt like you were setting the road on fire (though it did feel entertainingly quick).

 

I'm just in the running in period after a rebuild (only done about ten miles so far) and it will be interesting to see what it's like once fully run in and re-jetted. The engine builder's bill was just over £3000 and the result might be about 150bhp, give or take five hp. I took the engine out and re-installed it myself to save money.

 

Anthony

[SteveP]

Anthony,

 

Would be most interested in your opinions on your rebuild once fully run in. Did you have any other mods done at the same time, such as 3D mapping perhaps?

 

SteveP

[Coose]

SteveP - 100bhp at the wheels is to be expected, as it seems that drive/transmission losses of 30bhp can be expected from a se7en type drive setup with these kind of power outputs. A friend of mine has a Sylva Striker with a stock Toyota 4AGE motor (on 40's) which is putting out similar figures to yours at the flywheel and wheels.

 

This might not seem impressive for a modern 1600cc 16v motor, but it's the way it does it - it revs to 8,000 rpm a damn sight quicker than my x-flow reaches 6,000!

 

Slanty Screen Coose

Gud ord bus!

[Klaus Loske]

Hi,

 

I have a fairly standard tune of the x-flow with revised head, forged pistons, nice bearings, 244 cam, 45 DCOE, 4-1 exhaust... pretty standard.

 

Thing produces 110 HP on the rolling road at the wheels (I was told that the RR is an accurate one becaus some serious racers use it) which is around 145 hp at the flywheel. 25-30% loss in the drivetrain is quite normal, so I am currently thinking to get a straight cut gearcluster to reduce the losses.

 

Before I had the car to the RR, I was very conservative with the rev limit at 6500 RPM.

Now we set it to 7200 and I must admit that it feels quite nice. The engine is really willing to rev that high. It even feels like it would like to do more but this would be asking for trouble, so I installed a rev limiter.

 

I also know the problem with the missing pull in 4,5,6th gear and solved it with a short diff (4.4:1). Top speed is reduced to around 200km/h in 5th at red line, but it now pulls verry willingly up to top speed. Had a battle with a 911 and it was hard for him to pass, only at speed over 150.

 

Klaus

 

1700+

Combustion is not a secret

[Klaus Loske]

Hi,

 

I have a fairly standard tune of the x-flow with revised head, forged pistons, nice bearings, 244 cam, 45 DCOE, 4-1 exhaust... pretty standard.

 

Thing produces 110 HP on the rolling road at the wheels (I was told that the RR is an accurate one becaus some serious racers use it) which is around 145 hp at the flywheel. 25-30% loss in the drivetrain is quite normal, so I am currently thinking to get a straight cut gearcluster to reduce the losses.

 

Before I had the car to the RR, I was very conservative with the rev limit at 6500 RPM.

Now we set it to 7200 and I must admit that it feels quite nice. The engine is really willing to rev that high. It even feels like it would like to do more but this would be asking for trouble, so I installed a rev limiter.

 

I also know the problem with the missing pull in 4,5,6th gear and solved it with a short diff (4.4:1). Top speed is reduced to around 200km/h in 5th at red line, but it now pulls verry willingly up to top speed. Had a battle with a 911 and it was hard for him to pass, only at speed over 150.

 

Klaus

 

1700+

Combustion is not a secret

[SteveP]

I do have a straight cut box (Quaife internals) and was always told that the losses should be less than a normal helical box, which is why 100bhp at the wheels seemed a bit low.

 

Anyhow, once it's been rebuilt it'll be on the RR again and I can get an updated figure.

 

Anyone know how much of the losses are attributed to the diff? I feel as though mine might be sticking a bit as when I turn the rear wheels at some point in the rotation it tightens up significantly and I don't think that it is brakes or handbrake fouling. All fluids have been checked.

 

Any other ideas as to what it might be?

 

Also, what would the 'standard' final drive ratio be on an 1989 De-Dion?

 

SteveP

[Joe 90]

A really important thing to remember is that rolling roads have very high tyre to roller losses, much bigger than typical tyre to road losses. This is caused by the double contact and the curvature of the rollers. If or when I build my next seven I will probably go for the 5 speed semi close ratio gears that came out a while ago. The ratios are good and the gears have a lower helix angle than normal. This is ideal for a road car, and much cheaper than a Caterham 6 speed box. I remember that road and race transmissions can source them.

 

98,000 miles so far

[ashaughnessy]

SteveP, I'll post something about my engine when it's run in. Might not be for a while yet...

I didn't have many interesting changes to the engine. Still on 40DCOEs, though I'll get it rechoked and rejetted when run in. I've now got forged pistons, 244 cam instead of 234, additional porting work on the inlet and exhaust manifolds and in the ports, and a whole pile of detailed changes to allow extra revs (probably to about 7200).

Anthony

[tom7]

In my time I've had 2 rear-drive Corollas, from where the 4AGE engine originates, this engine was rated at 124.5bhp at nearly 7000rpm back in 1982 - hardly modern!

This is a very respectable output for any 1.6 litre engine and is a brilliant bit of kit, bullet-proof although a bit heavy.

[bstark]

I have a standard (albeit rebuilt 5000 miles ago by Steve Parker Racing) 4speed xflow Supersprint and I would pretty much go along with Anthony on performance. 2nd gear can verge on violent and 3rd still produces very fast overtaking acceleration. Top end at brands GP a few weeks ago was an indicated 110-115mph twice per lap and none of the various 911s in my group were out dragging me, although I may have started with a corner speed advantage.

 

Based on the Brooklands days, 0-60 is around 5.5secs if you get it just right. Engine was rolling road tested at 120bhp at the wheels, but reading other threads these figures can vary enormously. I'm limited to 6000rpm by valve bounce, by the way.

 

Bob Stark

Supersprinter

 

Edited by - bstark on 2 Sep 2002 12:59:29

[Seven in SA]

Tom,

 

I have a 4AGE20V (Silvertop) in my seven, it rated 124BHP at the wheels when they were setting up my ECU and thats on a pants exhaust. You said the engine was a bit heavy, when mated to a T50 gearbox I am sure that mine came in lighter than the crossflow it replaced. It's a good engine but it is lacking a bit below 5000, the push when you hit 5g's is great but you have to change at 8500 from first to hit the 5g's in second other wise it almost feels bogged down at 4000 ish. Maybe mine needs a bit more attention

 

Nic

[Beej]

This is all quite heartening. I thought I had a major problem with my 1700 x-flow because it was struggling to pull more than 5,000 rpm in 4th (5 speed box) - although thanks to new chokes I can now get it to 5500 rpm. It seems I am not alone -its the old bhp versus drag thing. O well, I guess I need more bhp and less drag then. Does an indicated 110mph achievable on a sensible straight such as the one after Lavant at Goodwood seem average?

[greg]

Beej,

 

For a "standard" supersprint I would assume so.

 

For what its worth my old 150 bhp (118bhp @wheels) Quaife SCCS 4 Speed Xflow could pull an idicated 110mph in 3rd (so probably nearer 95 ish...) going uphill 😬

 

The medical term for wanting more BHP (or BHP per tonne as getting lighter is expensive) is called upgraditis, and gets expensive, is uncruable, or though budget restraints do make it benin.

 

Greg, Q 86 NTM (Green 185BHP XF)

[ashaughnessy]

I've never achieved more than an indicated 100mph in my car before its engine rebuild, with its bog standard supersprint engine, four speed box, and live axle. I would suggest an indicated 110 for your car is quite reasonable. The manufacturer's claimed top speed for the Supersprint is only 110, and that's presumably on a straight several miles long with a tail wind.

Anthony

[PeterS]

New7er

A few years ago I took my Supersprint to Roger King for a precautionary rebuild at 45,000 miles. I asked for it to be returned to standard spec., resisting the upgraditis. In those days, he didn't have access to a rolling road, so he directed me to one in Luton that he trusted. The result on track was excellent. I was still running Goodyear tyres so had everyone all over me on corners, but once on the straight when I pulled over to let them pass, they didn't seem to be able to make much impression. However, this was on a 4 speed box.

I had an electronic limiter set at 6000, which helped me to avoid overstressing the engine.

After a further 20,000 miles, I passed it on to the next owner, and it was still giving good performance.

The 1800 upgrade will normally ruin your already poor fuel consumption.

Talk to Roger.