Lotus Elan

Rolling Road adventures

PostPost by: pptom » Wed Jun 23, 2021 5:32 pm

I think I've finally reached the journey's end and thought I would post up some info of how I got here.
All following graphs were recorded at Northampton Motorsports on the same rolling road over 3 consecutive summers.

First up, the car (early +2) came to me having been sat for 25 years. I rebuilt the engine, bores were +40, I had them honed and fitted new rings. Also installed QED 360 cams with offset dowels and ultrasonically cleaned then rebuilt the carbs. Ignition running on an Omex 600 ECU.

IMG_20210623_180122_copy_1843x1382.jpg and


I knew re-ringing was a compromise as the block really needed liners, but couldn't afford it at the time. The following winter I had it lined and fitted Omega Std pistons, Also put it some QED 420 cams with the associated valve gear and adjustable pulleys. The graph shows 126bhp. I tweaked the cam timing and eventually ended up at 128bhp.
Lots of faffing with the Weber's, basically the QED advised jetting was quite rich, but I left with a plan.

IMG_20210623_180130_copy_1843x1382.jpg and


This winter I fitted some GSXR600 throttle bodies (£75 including injectors and sensors) a swirl pot, HP fuel pump etc etc. No other changes to the engine.

IMG_20210623_180139_copy_1382x1843~2.jpg and


The 'off the shelf' generic fuelling map felt much better than the old Webber's, post remap it feels a lot better, instant throttle response and pulls from very low down.
I have a final graph of Weber's (red) Vs Injection (black). You can see it now makes power much earlier, the carbs perform slightly better at 3-4k revs which is apparently due to the chokes and after that Injection just walks away with it.

IMG_20210623_180236_copy_1843x1382.jpg and


Drivability is much improved, no quirks or flat spots and it sounds awesome at WOT.
Out of interest, we upped the rev limit to 6750 for 1 run and it made no more power after 6500.
All in all I'd say it was worth it for me. The injection was a little project in itself which kept me amused through the winter and because I didn't splash out on fancy pants throttle bodies, it didn't really cost too much, should be better on fuel too.
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PostPost by: RichardHawkins » Wed Jun 23, 2021 7:01 pm

I had to look up what a GSXR is, apparently it’s a motorcycle.

A very impressive result, did you need to spend much after the initial £75 purchase price?

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PostPost by: pptom » Wed Jun 23, 2021 7:42 pm

High pressure fuel pump £50, swirl pot £50, fuel rail £40, inlet rubbers £100, pipes etc £50, probably in the region of £500.
A set of off the shelf Jenvey throttle bodies with injectors, sensors and a linkage would be getting on for £1500.

The biggest single expense is the ECU which must be getting on for £700 now. I started off 3 years ago with a cheaper, inferior product with the intention of using a computer for ignition only as a means of replacing the tired old dizzy. This gave me loads of trouble and in the end I sent it back in disgust and happened upon my Omex ECU second hand but unused. More money, but gave me the option for the future of using it for controlling injection too.
It really is a first class product.

The throttle bodies aren't a direct fit and there is a bit of working out and making bits, but that's more than part of why I did it.
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PostPost by: pptom » Wed Jun 23, 2021 8:09 pm

I think my biggest disappointment over the last 3 years was when I went to the rolling road after fitting the Q420 cams.
I know there are lots of variables and all engines differ, but found the supplied spec sheet was very optimistic in its claimed power and torque figures, the jetting specified was way too rich and cam timing was improved by going away from the QED specs and moving towards more conventional specs.
I forgot to mention that for the first engine rebuild the head was converted to big valve spec and ported by someone who knows what they're doing (not me!)
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PostPost by: miked » Wed Jun 23, 2021 9:10 pm

Very interesting. I fitted zx9r carbs last year with a Nodiz on 2l Zetec Elan and am pleased.
Since doing that i can not resist the temptation to go injection. £100 for zx10r 2004 Mikuni throttle bodies. As you say, complete with injectors and TPS. Nice and short and compact. Over winter i will do it with ME221 ecu. Already got an alloy tank so having mods to take HP pump and top mounted fuel sender while at it. Will be using a Danst manifold. With being Zetec there is a crank sensor and cam sensor as standard.

:D Mike
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PostPost by: miked » Thu Jun 24, 2021 8:07 am

Interesting about the qed cam timing. You would have thought it would be right from the Ken days.
Re my friends car and anybody going this route.
That crank tooth wheel sensor bracket that they sell is out of shape. A 6mm gap between the Ford sensor and their tooth wheel. Upon giving feedback to them, they said adjust it with an Irish screwdriver. A hammer, I believe. It would have just bent it out of line and not in a million years would the gap close. I made my own adjustable. What do they say?
Feedback is a luxury.
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PostPost by: 2cams70 » Thu Jun 24, 2021 10:28 am

Interesting results. Did you use the same ignition map for carbs and injection and did you optimise it to suit the cam change?
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PostPost by: pptom » Thu Jun 24, 2021 12:05 pm

I think there were minimal changes in the ignition map between the cam changes which did surprise me a bit at the time
Some minor ignition tweaks yesterday, mostly to try and find the cause of the torque drop around 5k revs to no avail.
I must admit, I was keeping my distance a bit what with Covid and I know how annoying it can be when people talk to you when you're trying to work. As much as I want the know exactly what is going on I didn't want to keep interrupting his flow.

With regard to cam timing, I ended up at the figures Rohan suggested in this thread:
viewtopic.php?f=39&t=46560

Pretty sure this graph shows the change

IMG_20210624_125758.jpg and


Qed Valve timing in red, 107 in 110 ex in black.
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PostPost by: 2cams70 » Thu Jun 24, 2021 1:36 pm

Thanks - interesting. That's the problem when you buy parts from the likes of QED and Burton's these days. The guys that were around in these companies when parts like this were originally developed are long gone. The expertise to properly support them at a technical level is no longer there. Development of parts for ancient old engines like Twin Cams stopped long ago and so they have essentially just become retail outlets.
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PostPost by: promotor » Thu Jun 24, 2021 3:06 pm

pptom wrote:Some minor ignition tweaks yesterday, mostly to try and find the cause of the torque drop around 5k revs to no avail.


Although I would expect torque drop at the bottom end, could it not be the size of the throttle body internal size - ie 38mm or so - is causing a hole in the torque? In comparison I would expect a 140bhp engine on 40DCOE's to run no bigger than 34/35mm chokes so 38mm is quite a jump.
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PostPost by: pptom » Thu Jun 24, 2021 3:21 pm

Probably, that was the thought, it's all a compromise.
Throttle bodies are 40mm Bore. The carb run was with 34mm chokes which is probably why the carbs have a bit more to give in the 3-4k range and conversely why the throttle bodies pick up so much after 5k revs
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PostPost by: 661 » Thu Jun 24, 2021 3:53 pm

2cams70 wrote:Thanks - interesting. That's the problem when you buy parts from the likes of QED and Burton's these days. The guys that were around in these companies when parts like this were originally developed are long gone. The expertise to properly support them at a technical level is no longer there. Development of parts for ancient old engines like Twin Cams stopped long ago and so they have essentially just become retail outlets.

I know Craig Beck is continually developing things for his race engines and I imagine other race builders are doing the same. The App K regulations will limit what might interest them
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PostPost by: Pfreen » Sun Jun 27, 2021 12:50 pm

I originally asked about the cam timing for the qed 420. During covid, I did a lot of modeling of the cam timing and determined that 106/106 was the best compromise between low end torque and peak hp.
I eventually bought the Kent cams L14 reground cams and set the cam timing to 106/106 with vernier cam sprockets.
I love it and I rolling road dynoed at 130 hp at the wheels at 6250 rpm.
I am not sure about the accuracy of the dyno, but the car drives great and pulls strong to the redline, 6750.
For reference, I have a Europa with a big valve, stromberg, ported head. It also gas headers, and two Hitachi 46mm Su carbs from a 240z.
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