Had my mk1 2l 8v (piper cam, flowed head, 3A bottom end) on the rolling road at TSR yesterday and it gave a disappointing 122 bhp. TSR said that it had a carb dizzy not an injection dizzy which wasnt advancing enough. So..... this morning gave the stealers a buzz and checked the dizzy part no. and my dizzy, part no. 026905205H is a 1983 GTI effort, which should be fine. Gave TSR a buzz, and they suggested making sure the rotor arm was advancing and springing back and to add a little oil to make sure it was ok. Checked all that and its all fine. Anyone have any suggestions as to anything else i can check regarding the incorrect dizzy behaviour? Its a good 15 horsepower down on expected power and feels pretty slow, but the power delivery is smooth. Was wondering what the three wires going into the dizzy do. I'm not very experienced with dizzies, and quite clueless as what the wires are doing as i thought the advance etc was all mechanical. Cheers in advance for any help
Only thing I can think of is that someone may have messed with the advance springs/mechanism. I would disconnect the vac advance pipe (and plug it) then run the engine at different speeds and check the advance with a strobe. I don't know exactly what you should get, but I would expect at least 20-25Deg at say 3000 rpm, if not more. TSR or someone here might know where you can get the advance curves. If you get no data, I'll go and check mine and see what it does. It's not new, but it's never been messed with. The three wires are just for the sender. They've got nothing to do with ign advance - that's all mechanical on a mk1. Just thinking about this more - if your advance springs were weak or worn, then you may have to compensate with dizzy rotation just to achieve idle advance. Then you could run out of advance at higher engine speeds. Is the dizzy very old or has it done a LOT of high speed running? I think it's really worth checking actual advance against spec curve.
My old mk2 driver had in 2lt tsr oulton with twin choke webber using 1.6cc dizzy from the old engine and that was fine it had 146bhp/158lbft torque when had rr at tsr. Not sure how much different your dizzy is from 1.6cc carb one.
Yeah I can see that that would be the most logical way to go. I think I'll ring TSR again on Monday and ask them to take another look. Presumably they tested the actual advance, saw that it was below spec, which perhaps was why they suggested that it was a carb dizzy. The advance spring(s?) don't seem particularly worn, the rotor arm appeared to advance and spring back adaquately. On the previous engine the dizzy worked fine, it was rolling roaded a few times and gave good results. But it hasnt been used for a year. I think I'll also try to acquire another dizzy to swap it out with, might save a lot of bother. Thanks for the reply.
So anyway, I fired up the engine this afternoon to have a gander, to immediately hear a hissing from where the vacuum pipe meets the inlet manifold. I'm hoping that this vaccuum leak meant that the dizzy wasn't advancing properly. Have yet to go on a proper run after fixing this air leak but ran her up the road and she seemed to be responding better. Hopefully this'll do it. Ah well, think it was definitely a friday afternoon effort yesterday by TSR as they also failed to hook up the vacuum pipe on the mk2 16v WUR I asked them to fit, rendering the whole exercise of changing it pointless.
sorry to burst the bubble, but the vac advance is purely for part throttle economy. it has no effect on the total ignition advance, thats all done in the dizzy with the centrifugal advance.
122atw... Thats not too bad IMO...Depends on whether the head is a Stage 1 or Big Valve Stage 2.. With a Stage 2 you should be looking at 130-140atw on TSRs rollers.. As a comparison my car makes 140atw @ TSR.. 2L 8v, BVH, Flowed Inlet & T/B, Schrick 276, AmD chip, 3.5Bar FPR, Supersprint 4 branch & system
nah thats 122 at engine chrismc! god knows what it was at the wheels, i'd hate to think. 155bhp from an 8v's very impressive! Edited by: ts295
OK, so centrifugal force does the ignition advance? What would i be missing out on then if i used the 3A dizzy which came with the bottom end? basically what exactly does the vac advance give me and can i do away with it by using the 3A dizzy? Man I'm sh*t at this kinda stuff, thought vacuum controlled the ignition advance.
vac advance gives you extra advance at part throttle and low rpm, basically for cruising fuel economy, and at a stretch midrange power. Edited by: 0ddball
So when you guys are talking about RR BHP figure, these are all AT THE WHEELS? This is quite impressive! So a standard 112BHP 8v will put out - what? - 90BHPatw? Hmmm....perhaps I need to do something about this!
wheels figures are useless. i run a dyno and they are upset by the gear you run in, the tyre pressure, how hard car is tied down, the ambient temp , the pressure, and the time your load the dyno by.. all a fudge really. Anyhow, a proper operator will do a advance curve plot at each rev and then you can get a dizzy tailored to suit. anyhow the peak figure will not be influenced at all by any dizzy as you can swing them all to give the timing the engine wants at that particulr rev.. the difference lies in what the curve is. Steven
Are you saying that you adjust the dizzy during the rr test, at different revs, to find out exactly what advance the engine needs? Then you should build a bespoke dizzy to suit the data you got?
just as useless as assuming coast down losses accurately represent the same power loss during acceleration too.
cost down losses done using dynoplot are mega accurate.. just ask someone who knows rather than the local pub expert- eg dave walker of emerald. he uses same system as me. Its so repeatable, you cant even fool it by running in a differnt gear and if you make a change you see where it affects it in other parts of rev range.. you cant do that with a non software system yes you build a besoke dizzy to suit the engine.. thats how i do it. Or if its on management then its a case of mapping. Steven
repeatability i'd definitely agree is where it counts. infinitely accurate bhp estimations ive gotten over years ago. but you wont convince me in a million years that a FWD box, drive shafts, bearings and tyres etc actually loose 50-60 bhp that ive seen in some cases. ive read daves diatribe that your probably on about, ive digested it, understand it, taken it all in. on the flip side ive read many others that give just as good arguments for wheel horse power and i'm indifferent with either setup to be honest. ive also spent about 8 hours at daves when he mapped a close friends astra and the same friends brother's golf gti racer. i'm afraid i'm not swayed with the info straight from the horses mouth either.
As said above TSR only give @ wheels figures so 122 is good in my books ( my car gives out 120 @ wheels, 168 @ fly on the last run) You wont get a priny out fron the lads at TSR as there rollers are old and cant do it. Why not try Tommys over her in wales (just 10 mins outside cardiff) he sets up grass track cars and rally cars. YOu will get print outs too GrantMS knows his stuff but you must leave him alone to finish my mates Rallye (over 18 months for a 20v T conversion!!!)
well, just chatted to TSR on the phone and got her booked in for next friday to have a proper look. Think it was an engine figure, i'd imagine it sounded a bit better than saying it was putting out 90 something at the wheels or summing! It doesn't feel like its going much faster than a standard 1.8 at the moment - was barely quicker than my e30 318is (139bhp, 129lb/ft) on the way home, so i'm pretty certain its not 122 at the wheels, i'd be happy with that! It's going to have a full session next friday so hopefully that will yield better results, TSR are going to take a proper look at the dizzy and fuel system.
