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#41 Re: rolling road figures
Posted: Fri Jul 05, 2019 8:43 pm
by 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!
#42 Re: rolling road figures
Posted: Sat Jul 06, 2019 9:10 am
by Tom W
politeperson wrote: ↑Fri Jul 05, 2019 6:31 pm
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.
#43 Re: rolling road figures
Posted: Wed Jul 10, 2019 3:33 pm
by 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.
#44 Re: rolling road figures
Posted: Wed Jul 31, 2019 4:10 pm
by H7OB
#45 Re: rolling road figures
Posted: Thu Aug 01, 2019 6:04 pm
by 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.
#46 Re: rolling road figures
Posted: Thu Aug 01, 2019 6:42 pm
by rswaffie
Sounds good - which rolling road did you use?
#47 Re: rolling road figures
Posted: Thu Aug 01, 2019 6:46 pm
by Heuer
Tom W wrote: ↑Thu Aug 01, 2019 6:04 pm
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
#48 Re: rolling road figures
Posted: Thu Aug 01, 2019 7:09 pm
by 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.
#49 Re: rolling road figures
Posted: Thu Aug 01, 2019 7:23 pm
by Gfhug
David, I get error 404 when trying to open that pdf you link to. both on a mac and an ipad
Thanks
Geoff
#50 Re: rolling road figures
Posted: Thu Aug 01, 2019 8:12 pm
by Heuer
Yes so do I - will check it tomorrow. Probably a cut 'n paste error from the master post on the subject.
#51 Re: rolling road figures
Posted: Fri Aug 02, 2019 9:05 am
by 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
#52 Re: rolling road figures
Posted: Fri Aug 02, 2019 9:36 am
by 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.
#53 Re: rolling road figures
Posted: Sat Aug 10, 2019 9:36 am
by Tom W
rswaffie wrote: ↑Thu Aug 01, 2019 6:42 pm
Sounds good - which rolling road did you use?
Sorry Richard, missed your reply. I used Project Heaven in Kings Cliffe.
#54 Re: rolling road figures
Posted: Sat Aug 10, 2019 9:41 am
by rswaffie
Thanks Tom. Is that the same place that Turrino Wheels have a unit?
#55 Re: rolling road figures
Posted: Sat Aug 10, 2019 10:53 am
by Tom W
I think it’s their paint-shop that’s next to Turrino, but yes, same outfit.
#56 Re: rolling road figures
Posted: Sun Aug 11, 2019 7:24 am
by Sarthe72
My Turrino wheels for the C-type. Beautiful work.
#57 Re: rolling road figures
Posted: Tue Aug 20, 2019 11:25 pm
by 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.
#58 Re: rolling road figures
Posted: Wed Aug 21, 2019 6:08 am
by chrisfell
Word around the paddock was that the engine made over 400bhp. Not sure where that number came from.
#59 Re: rolling road figures
Posted: Wed Aug 21, 2019 10:24 am
by flatfloor 3.8
chrisfell wrote: ↑Wed Aug 21, 2019 6:08 am
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.
#60 Re: rolling road figures
Posted: Thu Aug 22, 2019 9:58 am
by PeterCrespin
Probably wide angle heads for starters, plus billet crank and dry sump. That’s £25-30K in parts alone.