Backgrond story is, I had a cracked manifold, removed carbs and manifold to repair the exhaust crack. When reassmbled it ran like crap even to my ear. I tried not to knock anything out when removing the carbs etc. But something must have gone wrong? Took it to Novatec-R today, and ran the car on the dyno, last time on a dyno dynamics it made 165. This time it struggled with 100. They looked at venturi to se if they were twisted, plugs were fouled up black carbon, changed them, then started looking at the jets. It had 160 main F16 and idle had been drilled and ground so unknow. They changed jets to 150 and idles to 60, as lambda was showing lean bottom end then going rich. ALso noticed distributor was slightly loose in vertical movement on rotor, unable to source a new one as gsf unhelpful with PN supplied? Its a 1.8 8v ex John Mawdsley car, built by Ian carvell btw. The Hall plug is rectangle 3 pin. Back to problems, why did jets start getting changed to cure a rough running car when before it was sweet. End result was 135bhp which for a 4-2-1 twin webber 45's ported shrick cam'd crissle head car is ****e IMHO? The ignition also got changed from 24 deg down to 15deg but there may be a problem with the advance under revs? I'm all a bit miffed after today, and now have to race at the weekend with a down power car? Any pointers? chokes are 38's iirc. Will pull it all apart to get exact values after the weekend.
That is a large loss of output which suggests a significant fault. And 24deg to 15deg is a huge shift in ignition timing. Was this measurement taken at tickover or full advance? I ask this as the 24 is knocking on for what you would run as full advance (around 30 would be close to the mark), but 15 is more like a tickover setting for a tuned and cammed engine. Also if the inlet and exhaust manifolds have been off, are you sure the exhaust gaskets were installed the correct way round? The ones on cylinders 1 & 2 fit one way, and 3 & 4 fit the other. If they are wrong then the inlet manifold sometimes will not seat correctly as it hangs on the edge of the exhaust gaskets causing an air leak.
Dan has hit on something with the gasket/manifold alignment, so that needs checking for sure. Are all these power figures wheel or flywheel figures? If the dizzy is only running 15 degrees max advance under full load then don't attempt to run it as yr likely to melt a piston. Max advance should be from 24 up... my engines run between 27 and 32 subject to spec. A std distributor gives 26 degrees max advance on the std 6 degree idle setting. .So the 15 & 24 isn't working out unless the dizzy has been modded. If the engine has made 160hp before Im guessing that's a calculated flywheel figure..?...so it should show around 135 at the wheels. Unless the engine really needs it..160 mains is likely to be a bit rich on that spec and choke size.
Did you check compression and cam timing? It sounds like they haven't been changed, but it's always possible that you could have had more problems than just the cracked manifold.
Morning, quick post before heading up to Cadwell. The exhaust manifold came off but I split the carbs at the inlet so that part stayed on. Although I'm pretty sure the 4 gaskets for the exhaust mani went back on all the same way around. It's now set for 15 deg on tick over, before I think it was 24 they were fiddling about so quick with it, it certianly wasn't under full load with the 24 deg to start with. These are calc fly figs, so maybe I need to check that the two dyno ops are using same % value too? As MR HC says it was 135 atw. now I didn't even get an ATW fig all done at fly I think. I better check that lol or these figs are the same then!! Think it was rich on the 160's though as thats why they fouled up. Cam timing got played with and altered curve to bring power to top of rev range, running a vernier pulley. Didn't comp test, but engine is only rebuilt from the winter. Will check atw and fly for graph. Mr HC may well have to bring it SW as you and the website seem to be in the know THanks guys let you know how it goes.
I am assuming that the car was tested at Novatec-R before and measured 165bhp peak before? Note. A Dyno Dynamics dyno displays modelled flywheel power in "shoot out" mode. Correct torque quantity depends on accurate rpm input. Now on the same dyno and similar conditions it is 135bhp peak? If the car feels the same you now, even after tuning there seems to be a disconnect in measurement rather than thinking the car is down on power. It might well be "up". Can you post you plots for us to further understand what is happening. AFR will be handy too. If you do not want to post it up you can pm me and I will have a look at it offline.
Yr more than welcome...come on down. If you pick this message up before you race I'd keep an ear open for pinking / det. .Id bring the ignition back to 10-12 tops. I use 160 mains in mine with bigger chokes and 29hp more, so I'd expect yours to be rich on them. Cam timing needs a back true tdc found then find the split..start with the inlet 10-15 tho more and it wont be a million miles off. All the best with the race.
Hi, Sorry for the lack of reply, manic race weekend. Had a gear box go on sat practice, managed to source a std box and change it that night. Car ran well and didn't feel down on power, even closed down some Fiesta ST 2000 up Park straight so I don't think I can be down on power! Will double check tomorrow, but pretty sure the second run was done atw rather than fly. Timing is another new subject for me to get my head around though? no sound of det or pinking and used much less race fuel too. Only thing I didn't get to do was change to BP7ES from the 6's in there now. Can still stick up the dyno sheets before and after if interested?
Morning, Dson't worry the dyno guys told me tot to use the 6's but I ran out of time and forgot to try and grab some in halfords on saturday when getting mtf to change the gear box! I finished 7th overall and 1st in class, abiet only 2 in class. CSCC tintops from Cadwell, results here from TSL. http://www.tsl-timing.com/?loc=club...SCC&event=club&source=cscc2006&eventid=112764 Here are the before and after atw I believe. After, so not much difference other than the idle is alot smoother and it seemed to use alot less fuel during the race.
Well done! Cant be an awful lot wrong with it then. What class is that Alex? I've been looking at options to run mine.
The scale on went to 6500 and I think that is where they stopped revving it, maybe would of had more power over 7k but I dont take it much above 6500 anyway. I am in Class C, seems to be an odd class as not many cars for it right now, although the guy with the Puma said there are a few more Puma joining the series soon.
The peak power is at ~6600rpm in the "before" graph and at 6200rpm in the "after". Looks like the engine gained torque in the latter, hence the difference in feel. @racer66, I understand you are around 5 miles from me.
Every chance, but if it's winning without breaking it thats all you need to do. Whats the capacity then... up to 1800 with the Puma's beingat 1700?
Class structure: Class A: 1801cc to 2000cc (multi-valve) and all Turbo-Diesels Class B: 1801cc to 2000cc (8V) and 1601cc to 1800cc (multi-valve) Class C: 1601cc to 1800cc (8V) and 1401cc to 1600cc (multi-valve) Class D: 1401cc to 1600cc (8V) and up to 1400cc (multi-valve) Class E: Up to 1400cc (8V) Class I: Invitation (Not eligible for awards) Cars must run on MSA list 1A/1B treaded tyres
As Mr H says well done and I'm with him on the interest in the racing. Where do you get the regs and info for for CSCC from to have a look?
