Crossflow Supersprint How do I get more power

[Roger King]

Never done it so can't comment. What are the advantages, if any, over DCOE's?

[Ian Mackenzie]

For bike carbs have a look at locostbuilders, as far as I can see they are effective for the cost. Ok slightly different but the 2l duratec with gsxr throttle bodies, megasquirt (circa £600 for Ecu and throttle bodies should see around 190 bhp).

 

Cheers Ian

[Duckpit]

What about programmable distributors

 

http://www.accuspark.co.uk/Blackbox.htm

[Super_Rich_Bernie]

The programmable distributors (also look at 123 distributors here) are popular with a lot of classic car folks. They either come with a set of curves you can select, or with the ability to program your own. They are 2 dimensional though - the amount of advance is determined by engine speed only. Very easy to fit and set up - the pre-programmed ones don't need a rolling road session.

 

3d ignitions take a feed of throttle position, or manifold vacuum, so the amount of advance is determined by engine speed and throttle position. Having a vacuum unit on a normal distributor crudely does the same thing.

 

Whilst 2d units are an excellent replacement for a shagged out normal distributor, they won't do all the good things the 3d unit, suggested by Roger King above, will do. (though they would let you select a curve that gives optimal advance for wide open throttle).

 

I don't understand why 123 don't offer a unit that takes an input form a throttle pot. You could ask them if they plan to. I'm sure there would be a worthwhile market for x-flowers.

 

Jonathan

[George C]

A couple of things:

 

A really light weight steel flywheel is a cheap good upgrade and not too expensive but only worth doing with the rest of the bottom end. I had one (on a crossflow) with slots machined out and a small diameter clutch and it gave the whole car a much more exciting feel as the revs picked up very quickly. No problems with tick over either.

 

The 123 distributers look interesting but quite a few people don't get on with them, don't know why.

[Roger King]

That would have been a competition flywheel with a 71/4" race or rally clutch. They're wonderful, much lighter than a road set up, but a bit specialist and also not cheap.

 

The road type flywheel that Caterham fitted to the Supersprint is realistically just about as light as possible with a standard type clutch (it's one of the best things they made). Normally, I'd agree about lightening the flywheel as a very cost effective improvement, but in this case there's really almost nothing that can be removed safely.

[Duckpit]

last question, you hope 😳

 

Can I put the megajolt in with a base maP for a 7 & get better performance than I am getting now.

 

Problem is that we have no rolling road in the Channel Islands & I would only want to bring it to the UK once for rolling road after I have done the engine the following year

 

Nick

[Roger King]

Bearing in mind what you are now running, even that is likely to give a significant improvement. But you are taking a bit of a risk without testing its suitability. As a guide, I would initially aim for a map with no more than 34 degrees full advance on full throttle.

[Duckpit]

I lied

One last question

 

Roger wouldyou have such a map ?

 

Thanks

 

Nick

[Crudders]

What an interesting thread - thanks to all previous contributors.

 

If the OP has no objection, could we keep it going? The heading is perfect and the thread could be a very useful resource for anyone researching the topic in future, now that us crossflow owners seem to be in a dwindling minority.

 

I have quite a hoard of crossflow bits and would like to build up an engine producing a little more power (140+ ideally). The current spec. is pretty standard Supersprint - 1600 711M block with +090 overbore and 1300 pistons (making 1690 if memory serves), 234 cam, flowed head, bigger valves, twin 40s.

 

Can a 'worn' +090 711M block be bored again and if so, (a) to what, and (b) where would be a good source of suitable forged pistons? I know an AX block can take much larger bores but the cost of those is getting silly now.

 

What sort of power and tractability could be expected from a Supersprint spec with the addition of forged pistons, 244 cam and Megajolt 3D ignition, still running carbs? I like the 'easy' power delivery of the 234 but having driven a mate's 7 with one of Roger's 180+BHP 1800s running a 254, it may have been a little peakier than my old lump but I have to say it was awesome and very addictive 😬 I should have bought that car . . .

 

Keep the crossflow wisdom coming chaps

 

Cruds

[OliverSedlacek]

There are loads of maps on the Megajolt forum, so I would start with one from there. If you go 3D mapped ignition you need to decide whether you're going to use a throttle position sensor (TPS) or Manifold Absolute Pressure (MAP) sensor as your load signal (I use 'MAP' for the sensor and 'map' for the lookup table, but it's still easy to get confused). A MAP sensor is more repeatable from engine to engine, but not so easy to rig up to twin DCOEs.

[Duckpit]

Bike carbs

 

Advantages:

Due to the way in which bike carbs are

constructed they offer many different

advantages from their design.

Essentially, bike carbs are what’s

known as a constant velocity (CV) carb

which works differently to a normal

carb. It’s a more efficient and more

modern design that increases both

drivability and throttle response

through the use of variable sliding

chokes. It also means that when set up

correctly they can be more efficient

with what fuel they use, which in turn

gives better fuel economy. Plus, they

can be easier to mount on cars where

restrictive space is an issue as the float

bowls do not have to be dead straight

as they do with Webers.

Finally, there is the price — a bike kit

can be up and working very cheaply if

you are happy to source bits and make

what you can.

 

Disadvantages:

 

Due to the nature of CV carbs they

can be tricky to set up and not many

rolling roads understand them or are

even willing to touch them, so you

can be limited to where you can take

your car. Correct installation is critical

too; it can make or break how well the

conversion works as a package and

although bike carbs are cheap and

easy to find, new and replacement

parts are notoriously expensive so be

very careful what you buy.

[Roger King]

Sorry, don't have a map because the Megajolt post-dates (I think) my ceasing to build engines.

 

I don't know how flexible the Megajolt is in terms of components you can use with it, but Weber certainly used to sell a throttle pot kit to fit DCOE's when used with their Alpha system. It's really easy to fit and would solve your problems if it's useable and available.

 

The reason that MAP sensing is a problem with DCOE's is that each cylinder has its own entirely separate induction passage which all show strong pulsing when the engine is running. This can send the MAP sensor into a fit.

 

On a more conventional set up the induction goes via a plenum chamber to which all four cylinders are linked; this, plus the fact that it is a plenum chamber in the first place will smooth out the pulses to a relatively smooth pressure.

 

It is possible to connect all the induction tracts on DCOE cars with balance pipes to give a reasonably smooth 'aggregate' reading of all four cylinders, but I've never done it so can't offer any experience on the subject.

 

Ahhhhhh.............. Bike carbs are Constant Depression type - that would be S.U.'s then!

 

Edited by - Roger King on 26 Sep 2013 19:59:14

[CaterBram]

Weber do still sell the TPS & mounting kit

[Roger King]

Cruds,

 

You'd be really unlucky if your 711M wouldn't go to 83.5mm. This is only around .010" bigger than your Supersprint and is the size that many forged pistons run to give a true 1700ccm.

 

If you run a 234 with forgings, a suitable advance curve (be it 2D or 3D) and lots of other small things - higher compression ratio, improved flowing to the head, 34mm chokes, decent exhaust, etc, you should achieve 140bhp without too much trouble. It will rev to 7000rpm easily (I have to assume here that the whole engine spec is suitable for this) and if you have 3D ignition will also be tractable enough to plough fields with.

 

It's not the most powerful spec you can build, but it is an absolute delight and in many ways more fun than more power with a narrow power band. That said the 244 is nearly as tractable and gives around 10bhp more.

[Duckpit]

Ah, looks if my petrol pump is packing up,

 

Any advantage on an electrical one ? maybe 0.1bhp ?

[Crudders]

Thanks Roger, much appreciated To 234 or 244, hmmm . . . Naturally I have one of each, being an accomplished hoarder

 

The only 83.5mm piston of which I am aware is the Accralite 1015XC835, which Burton sell at £134.51 each. Are there others available/worth considering?

 

Cruds

[Crudders]

Duckpit - I built my car with a mechanical fuel pump and I think (it was a long time ago) I binned it after a couple of months. My problem was starvation at high revs and fortunately I sorted it before any damage was done. The Facet solid state electric pump that replaced the mech pump has been (touch wood) faultless. I also fitted a Purolator pressure regulator set to 3 PSI, which was then current Roger K recommendation IIRC

 

I don't think there's any power to be gained as such, but having sufficient fuel available at the carbs whenever needed is pretty handy, and makes starting from cold less of a chore.

 

Cruds

[Roger King]

Cruds,

 

Again, I'm out of date so don't know what is available, but the Accralites of my day were the ones I normally used. Gone up a bit though........

 

Seriously though, the ring pack is every bit as important as the pistons. The Accralite rings sealed better, ran with significantly lower friction and lasted much longer than the standard Supersprint ones. A win-all situation.

 

Bear in mind that a 244 will need more by way of work on the engine - valve springs, timing chain system, etc.

[OliverSedlacek]

A TPS on DCOEs is certainly available and works well with a Megajolt (it' s what I'm using). It will be easier to install than multiple pipes running from the manifold to a MAP sensor. You don't connect a MAP sensor to the plenum as that is upstream of the butterflies.

 

I was initially a little unhappy with the change from a 234 cam to a 244 cam because the bottom of the power band went up from 3000 RPM to 3500 RPM. This meant it didn't seem much quicker on the road, despite a big improvement at 6000+ RPM. However after mapping the ignition it now takes full throttle from 1500 RPM, and I don't see much point in considering the 234 cam.

[eric]

you never speak about the kind of head you will use : stage 1, 2 , 3 or full race

 

This means that the head is not so important ?

 

[cskip]

RE: Megajolt map. There are lots of maps available the internet for the xflow and other engines. There is a reasonable sized community using the Megajolt and they share there maps.

 

I am sure I have a safe map for a 244 Cam and a fully mapped, on a rolling road, for my xflow when it was running approx 150bhp spec (accalites, 144 cam). I also have a megajolt map for my 180bhp steel crossflow 😬

[Duckpit]

Thanks for all your responses CRUD or No Crud

 

Lets talk heads, what can I do to my standard head to improve performance

 

I have been looking loveingly at :

 

http://www.ebay.co.uk/itm/Ford-Crossflow-Alloy-BV-Gas-Flowed-cylinder-head-/280466077885?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item414d14b8bd

 

Still looking for circa £500 uopgrades so it keeps me going over the next few tears

 

But as you all have seen so far, I know nothing

 

Nick

[OliverSedlacek]

I haven't said much about heads because I don't have enough experience, and one outfit's stage 3 may be comparable with someone else's stage 5. There are a few points I can make though:

1. If you push valve sizes to the limit, the heads are prone to cracking. I'd normally go for one size down from the biggest on offer.

2. Check the valve to piston clearances. I learned the expensive way that this can vary if you change heads depending on how deep the seats are ground. It's probably not so bad when hardened seats are fitted.

3. Polished ports look pretty but don't count for much.

4. I'm currently looking at alloy heads and the jury is still out.

 

 

[George C]

If you look at the Burton website they have a nice selection of specs and prices for different heads including alloy ones. I don't think the stage 1,2, 3 etc means very much, you just need to get someone who knows what they are doing to make something nice. I would push the boat out and do it really well and then another year when you have some more money do something else - the bottom end or 3d ignition.

 

I don't have any experience of the alloy heads but I havent heard anything negative. They use them in classic Formula Ford now so they must be fine. I think they save 6kg or more which is a great upgrade in itself by taking weight from high up at the front of the car.

 

Also have a look at the Wilcox engines web site. These guys seem to know what they are doing but probably expensive.

 

Roger K built me a big valve head (cast iron) with narrow stem valves etc and its great, unleaded too. I have since upgraded the bottom end to all steel so have the Accralite pistons, polished rods etc, all low mileage if any use to you.