So I’ve managed to source a full 50mm system for my ’02 748s, which I’m going to replace the 45mm end cans that I bought with the bike back in the day.. My question is regarding the eprom chip that came with the 45mm end cans, specifically will the same one work effectively? I’m thinking not as the larger pipes will have an effect on back-pressure… If it will work, then great. If not, is JHP the best place go for a chip… I’m thinking yes!! If anyone has any info it’d certainly help. Cheers!
Eprom should work OK with a CO/TPS etc. setup, although it won't be optimal unless custom remapped but the 50mm system will likely give you less power than the 45mm.
Thanks for the info. As I'm a bit of an amateur when it comes to these things, can you explain when I'd get less power from the engine given only a slight rise in exhaust diameter? I'd have thought a slight increase in power, not much mind you, as it'll allow the exhaust gaese to escape faster, meaning the engine can ingest/mix and burn more air and fuel quicker, meaning more power...? Thanks in advance
Well you probably will have the same power, it will only shift up in the curve, so you need more revs. The feeling is that you loose torque, and you probably will. The best system for a std 748 is the 45mm. The 748R will probably benefit from a full 50mm after a remap, but sometimes also with an R the 45/50 is better. I'm interested dough in the 50mm system if you're deciding to sell it
The 50mm system is too big for a standard engine, even a 916/996 and especially a 748. So unless it's seriously tuned it doesn't give more power and even if tuned to do so it will only be at higher RPM at the expense of low-down. Many years ago I bought a 52mm system for my 916 but after researching never fitted it, so sold it on and went for the 45/50mm system which should give better results despite having done some tuning (gasflowed heads & increased compression ratio). I understand that desmoquattro engines seem to prefer a 'tapered' system (45/50 etc.) to a big-bore, whereas the testastretta respond well to big systems, although I'm not fully up on the physics behind it so someone maybe along soon to correct me...
I am currently running a 996sps full 50mm system on my 748R and have only had the throttle bodies balanced, the O2 corrected and a minor tweak to the onboard 748R open can chip RAM (or is it ROM) to try and smooth the fuel to air ratio throughout the rev range. It makes the same power as my 748sp based 853 (smaller valves) running 45mm/50mm half system but less tourque. It subjectively feels more responsive than the 45/50mm half system but it goes like the proverbial with both systems. Andy
It's generally reckoned that 50 mm is not the way to go with 748 engines. My son has a full race 748 by CJS and that only runs a 45 mm system, this was built for a specific, and now defunct, race series which had power limitations so was left at 115 bhp at the rear wheel. It is custom mapped but only by a power commander as when this was built the "technology" hadn't quite filtered down yet at that time. There was no question of using a 50 mm system. Here's a link to the Sigma Performance website, you can see graphs of the various setups and plenty of technical information. It might help. Sigma Performance - Ducati 748SPS Tech
Thanks for the feedback guys, certainly makes interesting reading - especially the link to the Sigma site. I'd heard about them years and years back. Sorry to see they've downsized, perhaps a sign of the times, but I'm sure the slipper clutch business is keeping them occupied. So, it appears it's probably the restricted inlet side of things that make the bike more suited (from a racing, top end performance pov) to the 45mm system. When it comes to tuning, is it the idea to have the inlet and outlet sides of the engine balanced in terms of size? The Sigma site seemed to suggest that all 748's have the inlet restricted at a dia of 44mm. Is this why a 45mm outlet (exhaust) works better in experience? I guess I have a couple of options, get them cleaned up and put them on (I'll never really see the difference as I'm no racer and I doubt it'll do any harm in the grand scheme of a road bike), or just box them up for the future. I've always fancied an 853 converstion - I keenly remember being spanked by a bloke around Knockhill who had an 853 converted 748, but he was a bit slower in the corners... made for a fun evening or two!! Nickmarieke: "I'm interested dough in the 50mm system if you're deciding to sell it " Not for the moment, but I like your style... ;-)
The 748 has restricted injectors, the 916 has a bigger bore downside of the butterfly. The 54 mm's of the 748R are too big if not set up properly as fuel sits on the butterfly and tips in under just off idle conditions hence the well known 748R stutter. The two best known conversions are the 853, the most well known, or fitting a 748R with stock 748 or 916 injectors, both are considered the best conversion Ducati did not make, they had different ideas centred around Supersport at the time. You are better off not using the exhaust, maybe selling it, get hold of some 916 injectors and then have it mapped fully by someone like CJS, your bike will then perform exactly as it should. If you are contemplating any tuning or gas flowing then get it done first and then have it dyno'ed and set up with a full custom map written into a custom Eprom. I have a 748R engine in a 748S frame and even under geared it is literally only 1 mph slower than a stock 748R, and no stuttering problems, so big is not always better.
FE, that's a great link. Here's some food for thought. Seems if I do some work with the cams, ecu and intakes those 50's will work rather nicely!! BikeBoy.org - Ducati 45 AND 50MM CROSS OVER COMPARISON
Indeed it does ;-) Last time I looked it was about the £2.5k mark. Will need to do more research at some point. Should make a great engine from what I've read.
