Crossflow Supersprint How do I get more power

[Duckpit]

I have a 95 Supersprint. I do one three day event per year and have managed to improve performance each year for the last 5 years until yesterday, ie weight, slicks, weight again & now a quaiffe diff.

 

Any ideas on how to get a bit more power from the crossflow at a very reasonable cost ??

 

Nick

[CaterBram]

Might be worth saying what spec & power you think your currently on

[Duckpit]

Standard 1700 Supersprint so I believe in tip top I would get 135brake

 

N

[Duckpit]

OR, nicked from another post

 

1700 Supersprint Engine Specification

 

Base unit

Ford ohv 2265E Kent crossflow

 

Bore Stroke

83.27mm 77.62mm

 

Capacity Compression Ratio

1690cc 9.75:1

 

Cylinder Head

Gas flowed and enlarged ports

 

Valves

Oversize, gas flowed design manufactured in 21-4N steel.

 

Valve springs

Heavy duty, Duplex with retainers to suit.

 

Camshaft

Caterham BCD with high lift short duration profile

 

Pistons

Cast aluminium modified to give valve to piston clearance.

 

Crankshaft bearings

Uprated competition type main and big end shell bearings.

 

Flywheel

Lightened and balanced

 

Clutch

Uprated competition cover assembly and drive plate.

 

Ignition

Caterham distributor with special side entry cap with optional Lucas electronic ignition. NGK B8ECS spark plugs.

 

Valve cover

Caterham cast alloy with "1700 Supersprint" script.

 

Lubrication

High-pressure oil pump with standard wet sump.

 

Inlet manifold

Caterham cast alloy.

 

Carburation

Two Weber 40 DCOE 151

 

Air filtration

Two K&N high performance air filters.

 

Performance Data.

Maximum power 135 BHP (99KW) @ 6000 rpm

Maximum torque 122/lb/ft @ 4500 rpm

 

Servicing Data

* Static ignition timing 10 degrees at BTDC

Valve clearances (cold) inlet 0.22" Exhaust 0.24"

Spark plugs NGK B8ECS

Spark plug gap 0.25"

Firing order 1-2-4-3

*Fuel 97 octane (4 star) leaded

Oil pressure (normal temp) 3-4 BAR

Contact breaker points gap 0.025"

 

Engines numbered with the suffix "UL" can be run on unleaded 95-octane fuel with static ignition timing of 14 degrees BTDC.

[Golf Juliet Tango]

Call Rob Morely at Ratrace. He has done a lot of work for Nigel Blandin (your near(ish) neighbour on Jersey.

He is a Crossflow afficionado and his expertise goes back to Vegantune days and his work on their DOHC head.

He squeezed a little more out of my AX blocked '96 vintage Crossflow, somewhere around 150?

[Drumster]

Might be worth mentioning that I have heard it said that the Caterham quoted 135bhp is perhaps rather optimistic. It was reckoned that my '93 Supersprint was nearer 120!!

 

I had a fair bit of work done on mine some 12 years ago by Roger King (who frequents here every now and then, but is no longer in the business) and that increased power to 140bhp and this was a very noticeable increase, thus lending credence to the previous paragraph.

 

I guess it depends on what you regard as a reasonable cost?

[BSA]

Call Rob @ Ratrace

[Duckpit]

Thanks all

 

By reasonable I mean circa £500 and/or something I can do myself like a cam change

 

N

 

[Drumster]

I think I'm right in saying that although the Kent engine was tweaked by Caterham it's generally accepted that the cast aluminium pistons aren't really satisfactory for extended periods of high-revs and are prone to expiring. My x/flow had Accralite forged pistons fitted and they currently come in around £136 each on Burton's website......

 

Upgrading a x/flow is not a cheap exercise. Mine cost in excess of £2k, but I did have the engine completely rebuilt and this also included a tuftrided crank, steel rocker posts, Lucas competition ignition system, rebore to 1800cc, the list goes on......

 

As has been said above speak to Ratrace....

[Golf Juliet Tango]

If you want advice for a DIY reworking (I appreciate the costs involved in getting the Seven or engine from Alderney to Hertfordshire), then find Oliver Sedlacek (a Club member, Penn Sevener and all-round top man) who has done a lot of work on his own high-mileage (well over 100,000 miles) Crossflow engined car. He will guide you through piston options, cams and injection options.

I'll try to contact him and guide him to this thread.

[Golf Juliet Tango]

Later, I will Blatmail you.

[Duckpit]

Thanks

[George C]

For the £ 500 budget I would concentrate on the head which you can remove yourself and then get a really good engine tuner to properly port, maybe some bigger valves, convert to unleaded, match to the inlet manifold. It all depends on what you have now but you would get a power increase from simply refreshing the head plus the other work will add to this. Some second hand Webber 45s would also work well. The bottom end could then be upgraded at a later date as your budget wont stretch to that at the moment. Don't worry about the pistons, if they are in good condition they will survive for the moment. Changing the cam is a relatively cheap upgrade but would lead to an expensive list of other things which would need doing so I would do that later.

[cskip]

Maybe the first step would be to get the current set-up optimized on the rolling road? (if you haven't already done so!) That would give you a baseline to start with.

 

If it was me, I would have to change the supersprint pistons for Accralite pistons, given the current pistons known failings. But that would blow your budget and give Zero performance gain.

 

For what it is worth, the xflow is a superb engine. I just sold my 180bhp 1700 xflow and I really miss the sound of the engine singing at 8500 rpm!

[bstark]

If you're still running a dizzy then a switch to Megajolt 3D ignition should be in your budget, and then get that set up on a rolling road.

 

Transforms the torque and driveability of the xflow, and makes the car noticeably quicker in most circumstances and against the clock on track.

 

Max power probably won't increase but you will get more of it more of the time, if that makes sense. .

 

Bob

 

[Roger King]

Yes, 3D ignition will make a big difference to both power and torque.

 

Assuming you have the Caterham "unleaded" distributor, you are running around 10 degrees too little advance at higher revs. Crossflows generally like around 35 degrees full advance on open throttle whereas that distributor tends to give around 25 to 26 degrees (they vary - a lot). That will give you more power, and the 3D bit, which cranks in more advance on part throttle, will provide significantly improved mid-range when not on full throttle. Believe me, you have to try it to appreciate the size of the improvement (I am of course assuming that it is mapped properly to suit the engine).

 

Next thing to do is change to forged pistons. The standard ones used in the Supersprint are seriously marginal in terms of strength for the application. Under no circumstances consider a cam change until this is done because you will stress them even more. However, the benefits of forgings don't stop at strength- they are significantly lighter which leads to better throttle response, and even more importantly, the rings not only seal better but do so with a large reduction in running friction. These things together mean that forged pistons alone will give you give a gain of 8 to 10 bhp. And of course they give you the opportunity to increase the compression ratio too, which will also help.

 

Changing the ignition and pistons like this will give you a freer revving engine with a very noticeable power gain at the top end while at the same time improving the bottom end of the rev range. Seems too good to be true? - try it.

 

Personally, I would advise the two above changes before almost all other work.

 

 

 

Edited by - Roger King on 23 Sep 2013 00:22:03

[Duckpit]

Thanks

 

I have an unleaded head running at 14 degrees advance, with aldon igniter and map.

 

If I put forged pistons in - do I also need new rods ?

[OliverSedlacek]

It's important to know how upgrades interact with each other so that you can plan them in a suitable order.

 

Forged pistons are a really good performance upgrade as they give substantially more power and reduce reciprocating weight, which improves acceleration. I was skeptical myself, but they really work. I don't know how much they cost these days, but it's obviously an 'engine out' job. You can keep your standard rods and crank as I doubt a steel bottom end is in your budget. When fitting new pistons, it is critical that you machine valve clearance for the cam you intend to run. If you plan to upgrade to a Kent 244 in the near future, make sure the cutouts are appropriate.

 

The cam has the biggest effect on the feel of the engine, and it's comparatively cheap, but also an engine out job. A Kent 234 or Piper 285 is fine for road work, but the Kent 244 gives a lot more top end. The main downside is you will need the valve seats machined to prevent coil bind, and the piston cutouts need to be deeper. Bronze guides and roller rocker do not give any extra power but do give respectable top end life.

 

The benefits of 3D mapped ignition become more significant with big cams and high compression ratios. It's taken me a while to get to grips with it, but it makes a 244 cam completely tractable for everyday road use. If you put a Megajolt system together yourself, it's also cheaper than most distributor based alternatives. I haven't been active on the Megajolt forums for a while, but what I'd like to see is integrated knock sensing. I'm planning to do that at some point, but not any time soon.

[Roger King]

If you have a distributor that needs 14 degrees it is almost certainly the dreaded "unleaded" version. This figure is what you set it to at idle, but bears no relation to the full advance figure at higher revs. If you check that, you will almost certainly see around 25 degrees - nowhere near enough.

 

The irony is that the so-called "unleaded" advance curve is completely unnecessary; in my experience a standard Supersprint runs quite happily on 95 octane unleaded with the original, correct, advance curve. Usual disclaimers apply to that statement, but the difference in performance is quite noticeable.

 

Some forged pistons are shorter than standard and need longer rods, but you simply need to make it clear that you want to run them with standard rods to make sure you get the correct ones.

[Duckpit]

Thanks Roger & Oliver

 

Things are getting clearer. maybe megajolt this winter & refresh the head & then piston next year.

 

Any improvement to the head while its off its done 20k maybe new springs ?

[nickh7]

Duckpit , take Rogers advice before you do anything else

 

Roger is to modest to say it but he built truly a stunning engine. He built a crossflow engine for a friend of mine and it was simply stunning with the most incredible driveability . It had 150 bhp but its flexibility meant that it acted like 190bhp . Enough to hand Jon ( a very talented driver I would add) 2nd at SPA and the lap record for his class at Malory and 750motor club wins against cars in much higher states of tune.

[OliverSedlacek]

I'm flattered to be mentioned in the same breath as Roger.

[andy couchman]

My engine spec is similar to that outlined above - forged pistons, Kent 244 cam and 3D engine management (with throttle bodies) plus lightened flywheel being the main changes. The engine is very tractable and produces just under 150bhp (and 120 something ft lbs of torque) and, on a recent tour of France and Italy returned over 30mpg (not bad for a crossflow...). It also has been dry sumped but no roller rockers (installed them but am not convinced they get enough oil to all parts of the rocker shaft when idling or in heavy traffic).

 

In hard performance terms the car's best run (no windscreen and all unnecessary weight cut out) was a standing quarter mile at Brighton of 13.5 secs and 103mph over the line.

 

One benefit of the crossflow is that you can update over time bit by bit. Which helps with the budget...

 

I'm no engine builder but perhaps pistons first, then cam, then 3D then dry sump? But Roger and Oliver may well have a more reasoned view.

 

Oh and the sound of a good crossflow being driven hard is still absolute magic to my ears! 🥰

 

Andy

[OliverSedlacek]

Budget is always a consideration!

 

If you can swing it, doing pistons and cam at the same time makes sense because the pistons have to be machined for the valve clearances and they both need you to take the engine out.

 

The Megajolt does at least save you money, as it should push your MPG up into the 30s (34MPG for mine when I checked it recently). I reckon that you make your money back in petrol in about 10,000 miles.

[Duckpit]

So what are your thoughts on a bike carb conversion ?