Rolling Road adventures
Posted: 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.