Crossflow Supersprint How do I get more power

[Roger King]

Properly done head work is expensive and would swallow your budget as the starter course.

 

You can certainly improve on Caterham's offering, but it is not the priority in your case. Ultimately, you could fit unleaded inserts, increase valve size, go for 9/32" valve stems, fit bronze guides, uprate the springs, fit titanium retainers and get the porting improved to suit.

 

I have never used the aluminium head so cannot comment other than to say that in my experience, most such replacement items have had problems. This may not be the case here, but I have no more knowledge. Unless something has been done to improve the porting I would suggest that the only real improvement would be the weight loss.

 

By the way, as others have said, "stage" numbers are meaningless; really nothing more than marketing hype. What matters is what is done - and whether or not it suits the rest of the engine spec.

 

Edited by - Roger King on 29 Sep 2013 19:54:44

[Duckpit]

Roger

 

Please could you tell me how uprated valve springs improve performance & if I would get improved performance by just uprating springs. I was thinking of refreshing top end this winter & valve springs may not be too expensive

 

Thanks Nick

[Roger King]

Uprated valve springs won't improve performance, but they allow other things that can. For example, if you go for a hotter cam it will almost certainly need different springs to accommodate higher lift and revs. Even the same cam might need improved springs if you do other work to the engine that allows it to rev higher.

 

This goes back to my point in my previous post that mods have to suit the spec of the rest of the engine. There is no "right" spec, just the correct one for the situation.

[Duckpit]

All

 

By the looks of things, DIY upgrade to a crossflow would be very hit and miss by someone of my expertise once I am past the megatron ignition.

 

So then there is the Zetec option. Am I right in thinking that my venerable Supersprint from 1995 would be more valuable as a crossflow than as a Zetec, after all it must fast be becoming a Classic.

 

Mtech seem to do a very nice Zetec 170bhp for £2,300 and every thing elses fits if you get the bearers and the 4to1

 

But I still love the crossflow 🥰 🥰 🥰 🥰

[Crudders]

Chris Alston (Aeroscreens) went the Crossflow > Zetec route not too long ago and I’m sure he’ll be happy to share his experience. Zetecs are available for not a lot (£700 brand new) but IIRC the cost once you have factored in all the ancilliaries that need changing to suit the 7 is more like £3k. As Chris found, you can recoup a good chunk of this on the sale of your old crossflow bits, especially if you have the highly sought after AX block. Some of Chris’s old engine came my way and I probably should have bought the block as well thinking about it, but hindsight is a wonderful thing . . .

 

I like the crossflow too and would be happy to upgrade mine with a set of Accralite forged pistons, a bit of machining, a head refresh and a Megajolt setup, but beyond that it gets harder to justify a crossflow rebuild against a Zetec. An ali head such as the ebay one you linked to above (which is bare with no valves etc. and is probably well in excess of £1,500 once ‘dressed’) is a lovely thing to have but isn’t likely to offer a huge improvement over an upgraded iron head at a third of the price – you are into seriously diminishing returns at that level.

 

At the end of the day it depends how much of your current engine you need and/or want to replace and how much power you are after. A Zetec with no internal modifications whatsoever will offer 160-170 on carbs, be very reliable and offer loads of torque. But it won't be a crossflow

 

Cruds

 

[Duckpit]

Hi Guys

 

Have any of you looked at Aldon Amethyst 3D mappable ignition, good firm so your thought would be good.

 

Nick 😬

[Richard K]

Here is a link to the Aldon "Amethyst' site here

 

You just need a suitable TPS

 

I already have the Aldon ignitor electronic ignition unit that works well.

 

NB Ebay price £180.00 😬

Richard

[Duckpit]

Richard

 

On the Aldon site they are doing it at £150

 

http://www.aldonauto.co.uk/shop/product.asp?P_ID=800

 

They also do the TPS.

 

I also have the Aldon igniter, it works well compared to points, but the timing is pretty bad

 

I was hoping someone had used the Amethyst, All I can find is that it would not be as good as the megajolt because of slap in timing gear, but it has to be much better than a non programmable 2d ignition. Its also half the price of a megajolt and you can easily fit yourself

 

N

[Eugene]

I went the 2L 210BHP Zetec route a while back...

 

See: Eugene here

 

With 45 Webers it's still just like a X-Flow, but with none of the drawbacks.

 

As far as best value for you pound I don't think you will better it.

 

And no, I really don't think anyone would pay a premium for a X-Flow seven... that's just not what 7 ownership is really about (I think).

 

And the conversion is something you could easily do yourself.

[Richard K]

Hi Nick,

 

The price for the TPS and Amethyst comes in at £285.75 with VAT and Shipping.

They add the VAT to £150 bring the price up to £180.

 

The Ebay site does free shipping. Ill check if they can also do the TPS.

 

Looks like this will become my winter up grade 😬

Richard

[Duckpit]

Yes they do Richard & will fit the O rings & clean your distributor for £15.

 

I'm lucky here I dont have to pay VAT 😬 😬 😬 😬 😬 😬 😬 😬 😬

[Richard K]

The "Amethyst" 3d ignition system and a Webber TPS have arrived 😬

Q. Roger says the ignition should ideally be 35 deg. Max at high revs. If the static timing is at 10 deg. Do I only need to ensure the system "adds" a further 25 deg.

 

The instructions recommend Max advance of 34 deg.

 

When I get it all fitted I will arrange a RR session. Just need get it running for now.

 

Richard

[Duckpit]

U r my hero, i am going to go for it as well

 

suggest u ring aldon who will give u good advice.

 

having looked at maps from the mega site they have advance on hard acceleration. Of 50 and more so i am confused

[Roger King]

Getting an advance curve precisely correct is a lot of work and requires the use of an engine dyno or rolling road. The good news is that getting it "about right" will be acceptable for most 7 owners. It's rather different if you have to meet European emission cycles.

 

In the old days of distributors (I'm talking about the centrifugal advance mechanism and ignoring the vacuum advance part here), the timing figure would simply increase as the the revs rose until the mechanism hit a stop and went no further. Basically the mechanism consisted of pivoted weights flying around, but restrained by springs; the higher the engine revs, the more the weights overcame the springs and therefore the more they moved from their static position. This rotated the baseplate of the dizzy which caused the contact breakers to open at a different point relative the crankshaft position - in other words the ignition timing advanced. Sometimes a bit of "sophistication" was found, such as using two springs of different strengths and lengths so that advance would happen more rapidly at some points of the rev range, but the basic principle was that the higher the revs, the more advance, until the stop was reached.

 

This was the best that could be done mechanically, but in reality, on full throttle, an advance curve usually needs to advance until the engine nears peak torque. At this point, it needs to retard a little, before advancing again once peak torque is passed. Easily done with a mapped system, which means that you can now push the timing nearer to the limit without going too far at peak torque. But going close to the limit means that some people push their luck too far, don't allow for a dodgy fuel batch, and detonate the engine.

 

The vacuum advance mechanism is entirely separate from the centrifugal system and simply cranks even more advance on when you are on part throttle; this is exactly the same thing that is achieved by the 3D bit of a mapped system, albeit that one uses manifold vacuum and the other uses throttle position as the signal. Since the manifold vacuum is directly related to the throttle position (at any given revs and assuming the engine is not supercharged) the two can be seen as providing the same information in different ways.

 

The reason you have this 3D/vacuum bit, and also the reason that the centrifugal advance needs to retard at peak torque is that combustion gets faster as cylinder compression pressure increases. On wide open throttle the cylinders fill with air relatively well and thus much higher compression figures (and therefore faster burn rate) are the result. On light throttle, the throttle is literally throttling the air supply to the engine so that only a little gets in; thus the pressure as the piston comes up on its compression stroke is lower and the burn is slower. You therefore need to ignite the mixture earlier to ensure that it reaches its peak combustion pressure at the right time. Peak torque just happens to be the point in the rev range at which the engine fills its cylinders most efficiently (this is cam profile, induction and exhaust length, etc, influenced) and therefore generates the highest compression figures of all - so once again, not so much advance is needed.

 

Not many have the facilities or time to optimise the ignition map perfectly, but in reality a map for an engine of similar spec from a reputable mapper will likely be fine, and vastly better than a non 3D system.

 

Edited by - Roger King on 19 Oct 2013 20:31:48

[elan_fan]

Just to back track on the pistons (I'm a bit late to the party). Back in my xflow days a good budget way was to use Lotus twincam pistons with the crown machined down by about .050" to give you a combustion chamber. The burn is a bit dirty on tickover as there is no squish but it's not a problem. Gives you a nice light piston capable of plenty of revs and power.

[George C]

Roger - Thanks for the explanation on the ignition timing etc, very informative.

[Richard K]

Just a quick up date on The "Amethyst" 3d ignition system and a Webber TPS I ordered.

To complete the installation you will need a 3 pin Minitimer connector to connect the Aldon "Amethyst" 3d ignition system to the Webber TPS. Just need to solder it on

 

Its a shame that Aldon don't memtion this but is not hard to find. Got mine from here

 

Richard

[Duckpit]

OK all

 

I have bought the Amethyst, TPS and new fuel pump my mods for this year.

 

I have the same question Richard K asked, if max advance is 35ish degrees and static is 12 degrees when programming do i just add 23 degrees to get to max advance at 7500 ?

 

Next year my mods are the pistons and a Piper cam, then .................................

 

 

[Crudders]

Well I'm not at all clued up on the Amethyst (yet) but my mechanical only advance is set to 10 degrees static/idle and 35 degrees at revs (can't recall the engine speed for max advance at the mo) and I wouldn't expect the electronic setup to be all that different. So yes, add 23 to get 35 max.

 

I can't imagine 47 degrees ever being desirable but happy to be corrected...

 

Cruds

 

[OliverSedlacek]

It's hard to do a whole map in a text posting, but my full throttle ignition map goes like this:

RPM Advance

1000 15

1500 19

2000 24

2500 28

3000 32

3500-7000 36

[Duckpit]

Thanks Oliver,

 

Do you have a TPS ? if so what settings do you use ?

 

Nick

[OliverSedlacek]

I'm running a TPS and those are the full throttle timings. The problem with a GPS setup is that it's hard to standardise them and transfer maps between engines.

[Duckpit]

OK the Amethyst is now in and car running. TPS tomorrow and then a blat, but still not sure of the TPS settings

 

Fingers crossed

[Duckpit]

Not good, am sure TPS settings are wrong, it seems that the Amethyst is topsy turvy on vaccum and TPS ie high vaccum = 0" throttle angle but amethyst sets it out as if low vaccum=0" throttle angle.

 

Misses on hardish acceleration, suspect too much advance so the distributor is possibly not locked down adequately and centrifugal advance is working slightly as well

 

It did however feel fantastic for a little while at lowish revs 😬 😬 😬 😬 😬

[Richard K]

Hi Duckpit

You are ahead of me. I was running the standard dizzy just to get the engine run in.

Only covered 300 miles so far but have decided to give the Amethyst a go.

 

Removing the distributor I could not 'get inside' to lock down the advance mec.

I was close to rounding off one the x head screws so have decided to sent the unit away to Aldon.

Richard