justaguy

Just reread your avatar says London. Sorry next time I'll try and be a little more observent

Lizard928

I've met Alex a number of times and he's a great bloke.

john gill

Hello all

Great build , will have 2 of mine complete this year, one in the GT road car and one in the race car . Both 5 litre, interesting on the comments on the maximum lift , for those that have gone someway to measure this , has their been any estimation of the maximum lift of the cams in the standard unmodified heads ?

As I am a fan of the supercar series here in Austrlalia particularly as they now have opened it up to other manufacturers , with the car of the future platform , they achieve 650 hp from a 5 litre with 10 - 1 compression , and big cams , interesting to know what we could achieve with these 5 litres ?

Not meaning to highjack the thread , happy to start another thread of conversation .

Speedtoys

Cool Colin..hoping to meet him sometime between the 19 and 25th when Im over there for "work" on the way back from Sweden the week before.

john gill

Actually for those of you that havent undertaken this track, it is amazing the time it takes to build a good engine and tune it , I know that a crate supercar engine (current GM or Ford) is $100,000.00 AUD .
Not surprisingly and are guaranteed from what I am to understand , within the engine speed and hours run . Outside of this they are meant to be rebuilt .
Very intersted in your pistons though , care to share ?
I went down that route , with the same piston manufacturer also , but the agent here found it all to hard , so ended up with the earlier pistons , which will give 11- 1 .
Thanks for the write up.

GregBBRD

Looks great, with great results!

Cheburator

I don't mind sharing at all, but I cannot be really specific as I left the choice to JE... I sent an old GTS piston to JE's agent here in the North of England, so they got an idea of what the basic is. Then the GTS piston was 3D scanned to super high tolerance. The CAD file was emailed to JE in the USA. We left it to them to compare existing pistons they have as forgings and the 3D CAD file of the GTS one. I had already given them rough parameters that I was working with - desired compression ratio, maximum engine rpm etc, expected power, torque, stroke length etc. JE came up with the appropriate piston design and coating for the alusil bores. I had them briefly in my hand and they have shorter skirts than the GTS and the crown is flat, with cut-outs to accomodate 39mm intake valves. They are lighter, but allegedly stronger than the OEM ones. Unlike the OEM pistons, the gudgeon pin is not offset - we were not after a smooth engine, and there were some time/costs savings to be made. The rings were supplied by JE, and were the approriate ones for an alusil bore, with the tapered end, where it was needed.

I know nothing about piston design, thus figured out that JE, being the biggest non-OEM maker of pistons in the World, probably is better equipped to advise on what works and what does not.

Their agent in the UK was great - delivered everything on time and to budget.

I am starting the build of another race engine - this time a 6.2ltr (maximum allowed in the VLN/RCN at the Nurburgring) - I think this time I will have the block sleeved with Darton or custom made barrels and use non-coated pistons... But that is another topic.

Going back to the power - there is certainly more power to made - we will not rest till we get closer to 100hp/ltr. Sitting at 88hp/ltr now...

I think, and I might actually offend some people on here - the LH/EZK is a bit slow, but the adjustability is phenomenal. No one by the looks of it has actually explored it, or if they had, they have not divulged anything, but the myriad of maps avalaible is just plain confusing. Stay tuned...

Hilton

Couple of things - I can't see a FPR in there, unless you've reversed the fuel flow from rear to front and lost the dampeners? Or is it hiding under the rear of the fuel rails?

Second - looks like you've repurposed the plastic throttle wheel to pull the actuator arms on each bank of the ITBs? I'd be wary of placing that plastic wheel under stress like that - my experience is they're fairly brittle, and drilling it for bolts will introduce stress risers.

Cheburator

FPR is where it is supposed to be - right at the back of the engine, but because we had them somewhat remodelled, you cannot see the FPRs anymore...

Hmm, food for thought on the throttle wheel - not really a problem to have a new one made of aluminium, but we thought it would be a shame for the Porsche plastic one to go to waste... Moreover, I have one in the garage with about 260k miles on it without any probs. Either way, I will have a new one made, and keep it as a spare...

ptuomov

A couple of questions and comments:

What's your redline for the engine? Right now, the power is peaking at about 6300 rpm. I think that with the current output curves, you want to shift pretty close to 7000 rpm, no?

If the redline is at about 7000 rpm, my (uneducated) first guess is that you don't need longer duration cams. More aggressive cams perhaps, in terms of acceleration, but probably not longer duration. If you're willing to spin it say to 7500 rpm, well then that's another story.

My 5th grade math says that you want to open the valve as quickly as you can to about 9.5mm lift ((pi*((39mm/2)^2)-pi*((7mm/2)^2))/(2*pi*(39mm/2)) = 9.44mm. After that, the intake flow should be relatively insensitive to more lift, although I am sure you've got the flow bench numbers to tell you this much more precisely than my 5th grade math.

The spring issue is interesting and important so you guys should figure that out.

Does anyone have a Cam Doctor files of Colin's Stage II cams? The *.c1's would definitely make the spring issue easier to model. If you end up needing new springs, my personal (untested and uneducated) view is that the PAC-1523/1223 springs from Peterson American Corporation with the custom set load, PAC R312 retainer, Ferrea SL-1066 locator discs, and VW lightweight hydraulic lifters is one reasonable option to consider. PAC will set those springs to your requested load and they will install at about 1.400" length. They'll coil bind at 0.900" (i.e., 0.500" lift if installed at 1.400") and PAC says they are safe to 0.950" (i.e., 0.450" lift if installed at 1.400").

The standard reminder: I don't know what I am writing about, so as always nobody should consider my writings as anything else but questions with a lot of unintentional comedy potential.

Speedtoys

I HAVE a cam doctor. Will measure stuff....

simos

That is nice piece of engineering.

The full race cams will be right way to go. I remember making some simple calculations for 5,6L engine, with 39mm intake valves for both Stage II and full race cams.
It may be hard to go beyond 500ehp with Stage II. Since you have MAP instead of MAF, 928 Intl headers and ITB's, the reason for not going over 6300rpm must be cam/valve area.
(the max. power is coming now at 6300rpm, perhaps engine isn't breathing enough) 500hp/5,6L = almost 90hp/L. You also need few degrees overlap to get extra boost. There is bunch of power still hiding.
Just make a new cam deal with Colin and you'll be happy

john gill

My target is 100kw per litre , I am a little amused at the mix of imperial and metric !

Vilhuer

AFAIK GTS valve springs are same as S4. They can be installed so that they are longer in extended state by using thinner lower seat. That way they wouldn't bind so easily but will they then be too loose?

Cheburator

The engine is 5.5ltr

This is the first tune - we are going back for more time on the dyno. It was done in the space of 4hrs dyno time, starting from scratch. There is more stuff to do - we need to iron driveability issues - at the moment throttle response is waaaay too sharp and it is just impossible to park or do a race start without abusing the clutch. I don't have it to hand, but it appears car is running a little bit too lean in the mid range, while there is plenty of fuel up top. Strange problem to have, but there you have it. It was also mapped to run Shell V-Power 99RON (no idea what that is in US numbers) in Bulgaria, which is frankly rubbish, but we went with the lowest common denominator to be safe...

Good info on the cams - maybe able to work something with Colin indeed...

I have no plans to spin it beyond 7000rpm - eventhough the new lightweight pistons can easily take the higher engine speed, I think the GTS crank and 2R rods will not. At present the fuel cut off is set at 6750rpm. I have a set of VW lifters lying around, maybe we should put them in... As one British supermarket chain says "Every little helps"...

Alex