Does that sound right? I was making 106lb/ft peak with the DMTL and now it's only doing about 102 peak. Granted, torque tails off a lot later and a lot slower so there's in theory more "usable" torque through-out the rev range but I was just hoping for a higher figure. The guy working the rollers said it was cos the car had been on the dyno for a couple of hours but I thought the hotter the engine gets the better it's supposed to run. Could something else be at play here, such as incorrect carb tuning or wrong trumpets? One of the carbs isn't running a trumpet at all because it's too close to the brake servo but I couldn't imagine it making that much difference.
I understand cool intake air but when my car goes on the rollers it takes a couple of runs to reach its highest power output and then it'll keep scoring consistent figures, which suggests the engine likes being warmed up? Or maybe that's just the way the rollers work
stinking hot engine bay wont help at all...their fan wont be as good as stinking along the motorway so what are the figures before n after...id have thought it would be way better with 40s
Hot (within reason) engines are indeed more efficient, owing to a reduction in the amount of heat energy from the combustion events going into the engine metalwork, and therefore being able to power the pistons better. Heat flow being strongly related to the temperature difference between the hot thing and the cooler thing, the warmer the walls of the combustion chamber the less 'wasted' heat transfer. [/thermodynamics lesson] Intake air temps do want to be as cold as poss. for max. volumetric efficiency though. I'd imagine that the warm intake temps, and your lack of a full trumpet section in your intake orchestra is why it's not as good as you'd hoped.
Apply the theory of longer trumpets = more torque if you can. Try and relocate your servo a bit to fit the last trumpet aswell.
106lb/ft with DMTL (102 brake) 102lb/ft with DHLA (110 brake) but power is up. and the torque is more evenly spread. If it were really the heat generated from being dyno'd for such a long time I would've expected the power to be affected as well. Unless it is and I should be making well over 110? I want to fit longer trumpets but I'm not sure there's space...
Can't you try angling the carbs somehow to create more space for things like that or do you not want to spend out more on the fab work?
For efficiency you need a warm engine and cold intake air (so the air/fuel charge is more dense), so you might get a worse effect on the rolling road, as there's very little airflow over the engine (even if they're using a fan, it's not like an 80mph wind. What air filter(s) are you running?
Nothing at the moment. Undecided over socks vs twin filters, and even then not sure whether to go K&N pancake or something else. Dumb question but don't sidedrafts stop working past a certain angle? I don't think I could get enough clearance without affecting their operation by tilting the carbs upwards. They're currently at about 15-20' to the horizon they'd probably need to be 45'+ to clear the bulkhead with 60's and even then I'd probably need holes in the rain/leaf tray.
Post your dyno plots for both conditions showing more importantly torque and AFR. Would expect the carbs to loose low speed velocity and have less restriction as the engine picks up speed. On an 8v 1.6 motor I would expect the close exhaust manifold will not help!
Annoyingly don't have AFR for DHLAs am dying to know why torque always dips at 2500. Will get plots up when I get home you'd expect the hot exhaust Mani to affect power as well... What about balancing, or the lack thereof? Would that affect torque or only idle? Be good if I could take them to someone to have a look and check they're balanced and setup and working properly...
If the carbs aren't balanced properly it'll definitely reduce output. I'd have assumed the rolling road 'experts' would do that first? As a quick check, if you stick your head down over the middle of the carbs, and slowly open the throttle, does it sound like one is sucking harder/sooner than the other?
DMTL DHLAs I don't know about expert, I always call them "technicians" but he said he he'd tried. His exact words were "They don't want to balance up properly, I think there's something stuck in one of them. You should really have them stripped down and acid dipped" When I mentioned the fact I'd bought them "newly refurbished" he came up with the most pained expression on his face. I've since discovered that DHLA's should be sonic cleaned, and not acid-dipped because that destroys them. Annoyingly the only person I've found who claims to know anything about Dellorto's is on a bit of a break and not touching anything mechanical.... By the way, yes I consider 3lb/ft at peak significant considering it's the same rollers and same operator. It even had new oil and better petrol the second time around (DHLAs) And who else finds that plateau/dip at 2500 weird? It's been there since day 1 the RR tech thinks its down to the profile of the cam but it's still really weird
`what's the manifold design like? buy yourself a book on dellortos and check them over yourself. carbs are pretty simple affairs on the whole, and regular cleaning techniques should be fine, check all the progession drilling are the same and not gummed up, check you are getting full throttle, get the carbs balanced are there any vac leaks at the manifold joints, is the timing ok? does it have the right jets/air correctors etc. ring up aldon automotive or anywhere that still messes about with classic cars and they should be able to help
So you went to Uxbridge to get this tested. Right around the corner from real help then . Yeah the side draft carbs are doing what they should to me. May have a touch more for adjustabily.
Who, Torque of the Devil? =\ PE said the guy who started it used to work for them. Manifold design.. um like any other 8v twin carb one I suppose. Cast. Not polished or ported. Unfortunately I don't really have the time to study basic car mechanics when I should be studying cognitive ability, or the space in my shared one bedroom flat so would be great if I could just drop the car off with someone for a couple of days. I'm one of those horrible people that solve their problems by throwing money at it.
hang on you want 40s on an 8v golf but you don't want to mess with it yourself... modifying old cars makes so little sense if you aren't handy yourself
Does it? I like old cars they are fun to drive, uncommon and I love Golfs but just wanted a little more pep from the 1.6.... Please let's not turn this into another "built not bought" debate, it's not going to help anyone... So does anyone know someone who can at least try and balance them up properly for me?
