Eoin
Full Member
Posts: 101
|
Post by Eoin on Mar 20, 2018 21:02:24 GMT
Sent you a picture of the crank trigger mount. Looks easy on a stand, but changing the trigger in situ is tricky. The mount is supposed to adjust on front-rear slots, but I found it had worn away the end of the sensor over time. I got some shims cut that I could drop in to adjust the spacing and that worked well. This is the kit. thedubshop.com/products/dub-shop-exclusives/crank-trigger/type-4/
|
|
|
Post by Zed on Mar 20, 2018 21:13:12 GMT
Thanks for all that. Food for thought.
|
|
|
Post by Zed on Apr 1, 2018 15:01:44 GMT
So... AFR meter fitted. 2413cc Dell 40's .2 emulsions 34 vents 57 idles 145 mains Hardly warmed up but I couldn't resist a quick drive to see it in action. Lean cruise 12.2 so my idle jets are too big as suspected. WOT 14-ish which is maybe a bit lean but I intend to switch back to 32 vents as the 34's are a bit fluffy and though they allow it to rev more than I ever do, that's pointless. Idles work on manifold vacuum. Mains are related to venturi size. Down a venturi should richen up WOT (mains) without effecting the idles. Tomorrow I will change to 32mm vents 55 idles to start with Same 145 mains. Then down another idle size if it wants and I have some. This is promising, I drive lot at 30-40-50mph and barely any throttle, so down, down, down with idle jets should net me some mpg gains.
|
|
|
Post by chad on Apr 1, 2018 15:36:09 GMT
I may have missed it but why did you go to 2.4 litres in the first place?
It seems to be like Bill Blydenstein's large capacity Vauxhalls in the '70s.
|
|
|
Post by Zed on Apr 1, 2018 16:56:42 GMT
I may have missed it but why did you go to 2.4 litres in the first place? It seems to be like Bill Blydenstein's large capacity Vauxhalls in the '70s. When I realised that torque truly is glued to capacity and while you can get excellent high revving torque and horse power from a 2L, it's not much use in a heavy bus. I had a new type-1 race case ready for a big stroker type-1 and all the add on bits, but I'd have had an engine with no vw parts at all that would probably overheat and still be not much bigger than my 2L effort. It was cheaper, stronger, bigger and better cooling using type-4 parts so my engine apart from barrels pistons and conrofs is all pukka 70's VW parts. 2.4 is as big as is possible keeping the stock crank. If still bigger pistons was a possibility I'd have made it bigger. Size is everything in a heavy vehicle.
|
|
|
Post by Zed on Apr 1, 2018 17:07:07 GMT
It's now my view than anyone building a bus engine would be best served spending their money on capacity. ALL cams with more than stock overlap, which they all are whether the blurb call them "fast road" or not wreck the low rev torque. In 4th at 40mph mine is at it's most efficient. At 70mph it's at max power. What could be better? Problem is customers ask builders what the max HP will be and from the off they're on the wrong track. If a builder said he'd build a 2.4l with 100hp, nobody would buy one, more fool them because it would be ace, like mine. My 2020 made 135hp but it was shit in a camper apart from above 3000, 3500,rpm with your foot down. The 2.4 action happens 2000 revs slower, it's soooo much better.
|
|
|
Post by chad on Apr 1, 2018 17:29:36 GMT
Yeah - Blydenstein went for torque and driveability in his Vauxhalls, which were no lightweights. I think that he stuck with the standard cams but improved the heads, without doing much if anything to the valve sizes, and increased the capacity by about 15%.
The MPG of these was also pretty impressive for the time so I'll be interested to see what you end up with.
It's a pity the focus is on HP - I seem to remember someone saying that torque affects acceleration, HP top speed. I know that this is a very simplistic way of looking at things but feel that it broadly holds true.
|
|
|
Post by Zed on Apr 1, 2018 18:10:57 GMT
You have a certain amount of torque based on capacity. Max torque is where the engine is running most efficiently. HP is torque x revs so the further up the rev range you can get the engine to be at it's most efficient, the higher the resulting max HP number. If the engine, like my previous one, has it's max efficiency moved from 2,000 to 5,000rpm you have increased it's max HP by 2.5x which is impressive in the pub, but can be sure it's bloody inefficient at 2,000rpm and multiplying that inefficient torque by a puny 2,000rpm leaves fuck all.
|
|
|
Post by Zed on Apr 1, 2018 18:17:35 GMT
Or, you can leave it where it was (at low revs) so that as the torque drops off at increasing revs the HP is more balanced because the diminishing torque is multiplied by increasing revs. i.e. welly through the revs that you actually use 95% of the time. Im my case 1500-4000rpm.
|
|
|
Post by Zed on Apr 3, 2018 15:02:22 GMT
Soooo... I've taken out the main stacks. Switched the venturis from 34 to 32 (for later, they don't effect the idle jets which work on manifold vacuum). Changed from 57 to 52. Idle driving afr has changed from 11 to 12.8 - leaner, but still very rich. I'm aiming for the lean side of 14.7 as long as it still drives without spluttering. 16 or 17 should be possible with so little load and vacuum advance. It looks like I'm going end up with idle jet below 50 for sure, maybe teeny tiny ones. Not what I expected at all, I'm going to save soooo much petrol.
|
|
|
Post by pkrboo on Apr 4, 2018 11:13:08 GMT
Is it driving better as well though?
|
|
|
Post by Zed on Apr 4, 2018 11:56:07 GMT
Is it driving better as well though? No! I've completely confused myself! It turns out that I hardly use the idle jets, so it seems. Also it appears I don't have a lot of manifold vacuum and I'm loosing faith in jetting for svda assisted lean running. Something isn't right. Today I thought I'd try some WOT with 32/135 as suggested to me. I can't hear detonation but it's far too lean both WOT and fast cruise. So, I've decided that once I've driven to pick up some jets tomorrow (with the 145s back in) I'll take the carbs off, set the throttle plates as recommended on the samba thread, adjust the idle speed with the timing and see where that takes me. No regrets investing in afr though it's confusing me at the moment, I wouldn't be able to mess like this on a rolling road unless I owned it!
|
|
|
Post by pkrboo on Apr 4, 2018 11:58:43 GMT
Yes, the AFR gauge is a cheap investment compared to a rolling road, plus its real world driving you can do
|
|
|
Post by Zed on Apr 4, 2018 12:16:57 GMT
Yes, the AFR gauge is a cheap investment compared to a rolling road, plus its real world driving you can do This latest round of attempted tuning is costing me a small fortune so I must percy veer. Morgan vacuum carbalancer £70 Gauge £150 Exhaust £150 Sensor boss and welding £30 Extending sensor cable £25 Jets tomorrow £20 Total so far £445. Heading rapidly for £500 and it's worse than ever.
|
|
|
Post by popegregoryxi on Apr 4, 2018 20:27:39 GMT
Yes, the AFR gauge is a cheap investment compared to a rolling road, plus its real world driving you can do This latest round of attempted tuning is costing me a small fortune so I must percy veer. Morgan vacuum carbalancer £70 Gauge £150 Exhaust £150 Sensor boss and welding £30 Extending sensor cable £25 Jets tomorrow £20 Total so far £445. Heading rapidly for £500 and it's worse than ever. On a more positive note, it is making for interesting reading. I like learning from other peoples tinkering.
|
|