Can you post up your dyno plots? I've been on the rollers to get tuned three times now and I still can't work out why I have this flat spot in the power curve just after 2500rpm. It looks like this: At first I thought it was because of a giant fuelling hole where it ran super rich but I've change the carbs now and it still does that funny plateau thing. Is that just the way the cam is designed or more to do with the way the throttle is applied and the carb becoming bogged down? No other dyno plots for carb engines I've seen show the same flat spot.
Another related question, what kind of cam timing adjustments were people running with this cam? Mine apparently likes running really advanced. Really, really advanced. Like the vernier is a tooth out, and then set to max adjustment advanced.
what engine... looks good power wise if its a driver . is doesnt just affect your power curve look at the torque at 2750 also.. be good if you can elimate these flat spots.
Something not right with that... Set the engine to it's true tdc using a dial gauge, zero the vernier (i.e align the clamp bolts so they're in the middle of the adjustment) so you would have in effect standard timing. Set the cam timing to give equal lift at tdc on both the inlet and exhaust. On a cam like that I'd say it would split at around 0.120-0.130 thou @ tdc. You'll need to fit a dial gauge to the buckets on number 4 cylinder and turn the engine back to see what the tdc lift was, do the same on the exhaust but in the other direction and note the reading... add the two together and divide by 2 to give you your split point. You can run the inlet with a little more than the exhaust (advanced timing) or split it and then swing the vernier on the rollers, somewhere around 2-4 degree's advance will give a good compromise of maximum power and a good power spread... but if you just split it or with a little more lift on the inlet at tdc you wont be a million miles off.
It was the rolling road tech who put it a tooth off, to get more advanced. I have the graph of how it was before the vernier was fitted... Can't make heads or tails of it though. So that 92bhp is the first time I had the vernier put on and setup. Then I took it back for the DMTL to be rejetted and it looked the 102bhp graph in my first post. I don't think he did anything with the vernier it was aligned with the original pulley but set to maximum advance. Then when I went back for the third time to have the Dellortos fitted and jetted he decided to take the whole pulley off and set it forward a tooth, so now it looks like this: So all that seems to have happened is the flat spot being shifted 500rpm up the rev range... And yes, bizarrely I'm making less peak torque on the DHLA's than I was on the DMTL, but that's being discussed in another thread, which I see Mr. Hillclimber has already discovered. Yes the block is a 1.6L driver, head is a ported PB.
A tooth is something like 12-14 degree's, so I'd imagine the belt was a tooth out to start with... or the keyway is out on the cam. Either way, the power curve does'nt look that bad.
Doesn't the torque dip/power plateau bother you? It definitely bothers me... =/ Hence the desire to find out how other people with this particular cam are setting them.
just a guess from an amateur, but if the flat spot shifts up the rev range with more cam advance, is it possible this could be an inlet problem? maybe some sort of rev-related inlet pulse? are you running open trumpets, or is there a pulse plate fitted.. i don't really know much about this subject though.
It could be a combination or a number of things... trumpets as mentioned above, exhaust manifold style... compression ratio?... should be up around 11:1 on a cam like that... ignition advance...or a combination of all of the above... do you notice it during driving?
Yea it just doesn't pull as hard for about 3 seconds under acceleration. Mike_H said the CR should be up around 11:1 too. It's whatever the standard EZ CR is I think 9.1:1. Shouldn't be losing any compression cos the heads been rebuilt and skimmed. Is there a cheap n easy (quick) way to raise CR? I had a thought the other day could the reason for the cam liking so much advance be related to the larger inlet ports on the 1.8 head?
even if the head has been skimmed, the CR wont be anywhere near 11:1. an is option is to skim the block.
Sounds like the c.r could be around 9-9.5:1... in which case you'll never get the best from that spec of cam. No such thing as cheap where engines are concerned... the easiest (sort of!) would be to fit GTi pistons and then re-engineer it to give the correct c.r. Or, prob not what you wanna hear, but drop the cam back to something around 270 degree's. You'll loose a touch off the top but may (again, depending on the requirements of the engine) pull up the low & mid range... or live with it as is until funds permit to build up a new bottom end. Not quite the topic for this thread but what size chokes are you runnin in the DCOE's?
They're DHLAs I think 32mm chokes. I was actually thinking about going back down to a PB cam and selling the TSR202 to make some money back, do you think that would help the low end torque and power? I'm not a huge fan of taking it up to 7000rpm to be honest, just feels bad. Would the vernier still be useful with a standard cam? What's the biggest cam I can realistically run with my current engine? More interested in making what I have work better together than trying to play catch up
'ang on... I've just read this properly ... if it's a 202 cam thats a hydraulic profile, 268/272 split profile.. dunno why I had 280 degree's in my head, too much cam work of late myself... thats my excuse anyway! You wont need such a high c.r for that cam spec. Find the timing figures for the cam, i.e inlet and exhaust opening, something like 24/64-68/24... or along those lines... and the LCA angle the cam is ground on, and we can go from there. And what's the rest of the engine spec, is it posted somewhere?
Yes split 268/272, mike_H said it needed about 10-11:1 for optimum performance. Full spec is around somewhere but to save you time it is a 1600 EZ block 1800 PB head ported and polished by Vagobonds (standard valves) TSR202 cam 268/272' with Kent vernier pulley set to maximum advance (plus an entire tooth advanced) Twin Dellorto DHLA 40's I think 32mm chokes, jetted on RR (giving the 110bhp plot, above) K-jet distributor (Scirocco GT I believe) 4-1 stainless exhaust header Scorpion 3-box stainless exhaust I've tried hunting high and low for the full specs of the cam, can never remember if 268 is inlet or exhaust duration. TSR website is woefully sparse on information. The TSR Store website doesn't even list it! Or not in an easily/logically discoverable location anyway.
Found it!... what version of the 1600 is it?... there's 2 different types with different bore/stroke combinations. I'd imagine it's the later type... any idea if the bowl size in the piston? Also, what type of tubular manifold is it.... 4-1 or 4-2-1? And if it's on 32mm chokes you could find more low end power (which may fill up the hole in the curve) with smaller chokes, 30's or even 28's if the engine is making around 100hp. And is there a power at the wheels figure?
Yeah I was thinking about going smaller with the chokes. Will be having the DHLAs stripped, rebuilt and re-setup soonish because I'm not all too sure about their condition at the minute. The 110 figure is at the fly whp wasn't measured. Um it's a 90-spec 1600 so yes later type. No idea about the pistons. The header is a 4-1.
For a start your on the right lines re having the carbs checked, they may have been sold as "re-built" but that may have just been a clean up the sell them. There could well be a twisted throttle spindle if they wont indeed ballance correctly. You wont need 32mm chokes at that power level... drop down to 30mm and try from there. Your not a million miles off what it's likely to make in terms of peak power with that spec for a 1600. If your making a true 110hp then you should be showing around 90hp at the wheels. You could make somewhere around a true 115-120hp (so an honest mid 90's at the wheels) with that spec, "but" you'll need to get the c.r right, along with the correct cam and carb settings. Low end power can also be lost with too big a bore exhaust system and sometimes (but "not" always) a 4-1 manifold can cause a hole in the power curve. I've also seen in another post you dont have all the trumpets fitted... that wont be doing you any favours either. Even if you run very short trumpets for clearance, you must run trumpets on all cylinders... I'd try that first. I also see the overall power/torque is down at low rpm over the DMTL, which is not good for general road use... though the choke size is likely to be some of the reason for that.
