LeMans Spec Speed 6?

[dvs_dave]

So, what actually was the spec of the LeMans Speed 6 engines? Always lots of talk, but nobody actually seems to be able to offer a definitive breakdown of the alterations made over the standard Speed 6?

[Whitey]

Block modified for extra water cooling on Cyl 6, high quality parts used, ie pistons crank etc, cannot remember what else Jason at Str8 six told me a good few years ago now.

[tail slide]

As whitey says, Jason helped build them so knows if you ask. Apart from above main power difference was GT spec cams with extreme profiles but as with all full race engines not driveable below 4k rpm, so no good for us!

[dvs_dave]

So, lets compile a simple list with facts and prompts for the key areas:

1. Revised water jacket around cylinder 6 to improve cooling
2. GT race spec cam shafts (4k rpm+)
3. Lubrication system?
4. Head/valvegear design, geometry and materials?
5. Inlet and exhaust ports? Airbox and exhaust manifold?
6. Engine management/fuel injection system?
7. Pistons/rods?
8. Crankshaft?
9. Bottom end?
10. Engine capacity and rev limit?
11. Likely BHP/torque figures?

[tail slide]

But Dave - is there any point?

I mean, it was hobbled by a tiny air restrictor, and the cam would make it undriveable on the road.

[dvs_dave]

Only other than being interested and to share knowledge......which is the whole point of this entire website.

[tail slide]

dvs_dave said:

Only other than being interested and to share knowledge......which is the whole point of this entire website.

I'm guessing but would think that the finer details of the spec are not going to make it into the public domain for commercial reasons, as a number of suppliers are competing for rebuilt/enhanced S6 engine business.

[V8 GRF]

dvs_dave said:

So, lets compile a simple list with facts and prompts for the key areas:

1. Revised water jacket around cylinder 6 to improve cooling
2. GT race spec cam shafts (4k rpm+)
3. Lubrication system?
4. Head/valvegear design, geometry and materials?
5. Inlet and exhaust ports? Airbox and exhaust manifold?
6. Engine management/fuel injection system?
7. Pistons/rods?
8. Crankshaft?
9. Bottom end?
10. Engine capacity and rev limit?
11. Likely BHP/torque figures?

Speaking to someone who was *very* involved the mods where restricted to the crank and cams, with nothing particularily trick so as not to introduce issues. So just good quality 'standard' parts in what I guess you'd call a 'Blueprinted' engine.

As regards power remember race cars run with restrictors so he suggested power would have been capped at about 440bhp max.

[450Nick]

I remember Jason (Clegg) telling me about them a few months ago and he seemed to think that they were bigger (4.5L?), and had a hell of a lot of money thrown at them to make them reliable for LNT. And still didn't last! I don't understand why they didn't try and take the AJP further? It just seems like a better suited engine to racing...?

[yzf1070]

450Nick said:

I remember Jason (Clegg) telling me about them a few months ago and he seemed to think that they were bigger (4.5L?), and had a hell of a lot of money thrown at them to make them reliable for LNT. And still didn't last! I don't understand why they didn't try and take the AJP further? It just seems like a better suited engine to racing...?

How about a 32 valve AJP8 would it have been possible to do?

[450Nick]

Possible certainly, in fact I have heard before that Melling did actually make up designs for a 4 valve head for the AJP8. No tooling was made and no actual castings knocked out though so it would be ridiculously expensive to do now. If someone were to put up the £ for the tooling and remaining development work though, I would have thought it would have the potential to be a great engine!

[tail slide]

450Nick said:

I remember Jason (Clegg) telling me about them a few months ago and he seemed to think that they were bigger (4.5L?), and had a hell of a lot of money thrown at them to make them reliable for LNT. And still didn't last! I don't understand why they didn't try and take the AJP further? It just seems like a better suited engine to racing...?

4.2L, like mine but higher tuned

But remember that 24hrs frequently flat out is a big ask for any engine, let alone a new design with a tiny development budget compared to the years and tens of millions spent by Porsche/Ferrari. I'd say it's a huge credit to the engineers and teams that some of the engines did make 24hrs at a good race pace.

Edited by tail slide on Wednesday 26th May 15:09

[450Nick]

No denying that, but having developed the AJP8 in the Tuscan Challenge and presumably having a fair bit of experience of running them in race environments, it would surely have been an easier task to put one of these in the Le Mans racers? Not to mention the load of extra torque available and lighter weight/smaller engine package. Seems like a no-brainer to me??

[tail slide]

450Nick said:

No denying that, but having developed the AJP8 in the Tuscan Challenge and presumably having a fair bit of experience of running them in race environments, it would surely have been an easier task to put one of these in the Le Mans racers? Not to mention the load of extra torque available and lighter weight/smaller engine package. Seems like a no-brainer to me??

Suspect was marketing-led as the factory saw the S6 as the new direction, maybe an ex-factory bod can confirm. But don't think it was the wrong direction; after data-logging both on track last year, the 4.2 S6 does have slightly better acceleration than even a tweaked 4.5 AJP8. As it should with a 4v head.

[450Nick]

That is a larger than standard version of the S6 though, when datalogging the Tuscan challenge cars over the last few years I found that Cliff's T350R consistantly had something like 100bhp less than the Mike Saunders' 4.5 Cerb out of the corners. They had similar peak figures, but Cliff had to wring its neck to keep up.

Taking the engines past their original capacities should yield interesting results however. I've driven a couple of AJP Cerbs and one John Ravenscroft 4L S6 special and I have to say the S6 felt faster. I'm currently having a tasty specced 4.7 AJP built for the racer though so I'll be interested to see what that chucks out against a nicely built S6..!

[tail slide]

450Nick said:

That is a larger than standard version of the S6 though, when datalogging the Tuscan challenge cars over the last few years I found that Cliff's T350R consistantly had something like 100bhp less than the Mike Saunders' 4.5 Cerb out of the corners. They had similar peak figures, but Cliff had to wring its neck to keep up.

Taking the engines past their original capacities should yield interesting results however. I've driven a couple of AJP Cerbs and one John Ravenscroft 4L S6 special and I have to say the S6 felt faster. I'm currently having a tasty specced 4.7 AJP built for the racer though so I'll be interested to see what that chucks out against a nicely built S6..!

Your 4.7 Tuscan sounds like a deal of fun, the mid range will be huge - is APM building it?

I know Cliff struggled with the std S6 engines. After Jason Clegg's meticulous build with light internals, flywheel etc. some other tweaks and half a day's mapping by JR we ended up with a plump mid-range for good corner-exits on hills & sprints, torque curve looked good on Dom's dyno;

Edited by tail slide on Wednesday 26th May 18:54

[-Jamie-]

I think the LM cars had another set of injectors in the airbox

[450Nick]

No, my v8 is being built by Jason Clegg. He has a good rep but I don't think he's done a 4.7 before so hopefully he'll build it nicely! Can't wait to have a go with it!

[tail slide]

-Jamie- said:

I think the LM cars had another set of injectors in the airbox

in sealed airbox, to help fuelling at highest rpm I believe.