rolling road figures

[politeperson]

Would have loved to. Next time.

Surprised you didn't hear me racing a Porsche Cayenne S on the A3 at around 9.30am yesterday morning.

I was giving it the beans!

[Tom W]

Don't forget, those track 400 bhp XK engines make almost no power whatsoever below 3,500 rpm, cost the best part of £75k and might last one season if you are lucky. They are really suitable for racing only (unsurprisingly).

My point was that a mechanical distributor isn’t the restriction in making huge power. For me, the beauty of the more modern systems is the extra control you get away from wide open throttle. That’s where I’ve seen most of the benefits in drivability from what I’ve done setting up my engine.

I haven’t had my car on a rolling road yet. I’d be interested in doing a quick power run, just to see what it makes, but I think it would really benefit from a full tuning session. There’s only so far I can get tuning by feel at home, but it has come a long way from how it was when I got it.

Totally agree on the mapping Marak. If it’s a load site that can be driven at, or through, then the engine needs tuning for that point. I’ve heard good things about Emerald, and was always impressed by Dave Walker’s articles in Practical Performance Car mag. Unfortunately, I don’t think they set up carbs any more.

[Nbromfield]

After rebuilding the 3.8 in my car, and after a couple of thousand miles of running in, we put it on a rolling road to finalise the set-up for the carbs and 123 ignition. End result was 221 BHP @ 5200 rpm and 237lb/ft torque at 4100 rpm. Apart from the 123 ignition and a stainless steel sports exhaust and manifold the engine is standard. I was led to believe (not by the engine builder) that these results are at the high end for a near standard 3.8. Certainly over the next 12,000 miles it has proved itself a lovely engine, with plenty of lowdown torque but also a real appetite to rev which it did not have pre-rebuild.

[H7OB]

I’m just back from a rolling road session with Peter Burgess. My mate was on first with his modified MGB with a big valve head, Weber, cam etc, but it didn’t do quite as well as hoped. Mine on the other hand did great! Its done just over 1000 miles since a rebuild, has the ITG Maxogen & UE needles and a 123 distributor. It seemed to perform really well from the start with just some better fine tuning of the carbs required. One rich, one lean, one OK. Peter commented on how crisp and willing to rev it felt, when they can often feel a bit flat. It’s making peak torque at about 3250 and is flying at 4000! This equated to over 213 BHP at the wheels so closer to that mythical 265 than I was expecting! I was almost disappointed, expecting it not to be much better after the session but it really feels so much crisper and more eager now, despite the good start. It really wanted to go on the motorway heading home so I really had to apply some restraint! It’s the best money I’ve spent on the car so far! Enc some snapshots...

[Tom W]

I took my car to a rolling road today, as I think I’ve got as close as I’m going to by setting things up at home. It’s a scary experience watching someone thrash the tits off your pride and joy, but fortunately it didn’t blow up in the process.

The initial run generated 204.3 BHP at 4022rpm, and 371.20 Nm (274ftlbs) at 3203rpm. These figures are at the crank.

The dyno showed the main jets were slightly rich, so these were swapped. All the other basic engine parameters were checked and confirmed to be very good. A new set of spark plugs were fitted, as the ones in there were due a change. After a few runs and some experimentation, the final run generated 216.4 BHP at, 3996rpm, and remains pretty much at this value for the next 500rpm. Torque was up to 398.46 Nm (294ftlbs) at 3246 rpm. The torque curve is pretty flat from 1750 rpm upwards, having already reached 367 Nm (270ftlbs) by this point. This probably explains why the car feels so punchy.

I’ve come away with a few more jobs to do. There’s a low speed misfire that’s meant it wasn’t possible to properly map the lower end of the rev range. So, I’ve got that to address. There’s maybe bit of experimentation to be done with the air filters. The guys at the rolling road thought the end plate of the K&Ns were close to the bell-mouths h, so tried a run without filters, expecting to see a power increase. Refitting the filters didn’t reduce the power though, so they’ve stayed on for now. The ignition timing was checked too. Adding a couple more degrees didn’t make a difference to the maximum power, or introduce any pinking, so this was set back as it was.

So all in all, fairly pleased considering the engine is a bit of an unknown quantity.

[rswaffie]

Sounds good - which rolling road did you use?

[Heuer]

The guys at the rolling road thought the end plate of the K&Ns were close to the bell-mouths h, so tried a run without filters, expecting to see a power increase. Refitting the filters didn’t reduce the power though, so they’ve stayed on for now.

The problem is the sharp edge to the intake's either with the K&N's or without them. That is why the original stacks are so good - they have correctly profiled ends and the correct length to not disrupt the air flow. You might want to try the Mangoletsi filter on the end of the original inlets. Alternatively you need to fit the BCCP stub stacks inside the K&N's as in example 11 below

The reasons are explained fully in this document: and look like this:
https://www.dropbox.com/s/n9j1xoo7w4ycq ... s.pdf?dl=1

[Tom W]

My car is on Webers, so no standard intake system. The Weber intakes are similar to Number 10 in your diagram. The longer the intake runner, the better the volumetric efficiency at lower rpms. There’s a useful illustration of this for the XK engine in “The design and tuning of competition engines” book by Philip H. Smith. For a road car, the longer the better, it would seem, as this shows a marked improvement over the shorter lengths below 3500rpm.

[Gfhug]

David, I get error 404 when trying to open that pdf you link to. both on a mac and an ipad

Thanks
Geoff

[Heuer]

Yes so do I - will check it tomorrow. Probably a cut 'n paste error from the master post on the subject.

[Gfhug]

David, you are probably aware there are a few other links in the knowledge section that give similar errors.
An opportunity for Steve to learn how to do some housekeeping

[Heuer]

OK fixed!

The problem occurs because Dropbox changed their link addresses. I updated all the links in the Forum KB but there are instances where a document has been referenced in an old post with the old link. Not much I can do about it other than going through all 114,082 posts and checking them. I therefore rely on members pointing them out when they trip over one. As can be seen the process seems to work. If you notice any please PM, email or add a post to the thread concerned and I will fix it.

[Tom W]

Sounds good - which rolling road did you use?

Sorry Richard, missed your reply. I used Project Heaven in Kings Cliffe.

[rswaffie]

Thanks Tom. Is that the same place that Turrino Wheels have a unit?

[Tom W]

I think it’s their paint-shop that’s next to Turrino, but yes, same outfit.

[Sarthe72]

My Turrino wheels for the C-type. Beautiful work.

[64etype]

I've always wondered how much power is produced by the JD Classis E-type that shows up at Goodwood....and specifically how the engine is built and tuned. Anybody have the secrets? Is it a 3.8? Which gearbox? Rear ratio? I did a search some years ago when they beat the Cobras, but didn't find much detail.

[chrisfell]

Word around the paddock was that the engine made over 400bhp. Not sure where that number came from.

[flatfloor 3.8]

Word around the paddock was that the engine made over 400bhp. Not sure where that number came from.

The engine builder at J D Classics was a guy called "Piff", he was ex Jaguar Racing Dept. He told me at one of their open days that the engines for the racing Listers and E-types Etc made around 380hp.

[PeterCrespin]

Probably wide angle heads for starters, plus billet crank and dry sump. That’s £25-30K in parts alone.