The rod:stroke ratio is "the big argument" held by the Yanks about the ABF being so good. Personally, I don't think it's that important unless you're going all out and tuning pretty much everything. I don't know if anyone can look back through their archive of The Golf mags, but about 2+ years ago there was a white Mk1 with custom guards and really deep 13s (like ET minus 4 offset IIRC); it had a purple leather interior and sat really low. If my weird memory for this sort of things serves me right, the guy's name was Sven Zimmett. The car had a 2.0 16v with the absolute works, built by a place called Bauer Motorsport in Nurnburg (sp?). It was running 13:1 CR, something like custom Schrick 309/314 cams and spun beyond 10,000rpm. I've never forgotten the article but have lost the magazine. I've always wanted to build an engine like it, so am sloooowly working towards it... I remember them saying how it went madly quick (not surprising really )
Thats a good link. Having read through it a 15mm increase in rod length is only going to raise you redline by around 300 revs. Where are the other benefits? your reduced angle of sweep will deliver a higher torque curve with your longer rods but still is a long way from a 10,000 rpm monster. So what is required? or is this the problem to acheiving a high revving n/a 2.0l/2.1l 16v popping snorting monster
i think it also reduces bore stress and ultimately flex, as longer rods arent trying to push the pistons sideways as much. So id imagine you get less frictional losses and better seal maybe? when i was out in norway i was chatting to guys building tall block turbo motors, they were even getting rods made longer than the 159mm factory spec, and moving the pin up the piston a touch.
first of all cheers everyone and mk1driver for the pm'd ideas/info... but im stuck on some things,,,, people have mentioned these 85.5mm pistons but ive never seen them anywhere? 83.5 are the biggest ive seen? i dont think theyre should be a problem with the s/sprint 4 branch should there? and the rest of the system(magnex 2.5 inch)? this is whats making me lean towards going for 9a,having it bored for 83.5mm forged pistons,standard rod length but steel and balanced etc,steel diesel spec crank,lightened and balanced... it would be a true 2.1 and possibly? better spec than the bildon abf as that has cast pistons,but longer rods...????? whats really confusing me is,if i buy all the bits,how do i work out what needs machining where? for example,the forged high compression pistons,being higher comp,surely im gonna be near or hitting the valves especially when using a longer stroke crank too... and then higher lift cams... i cant get my head around it all...
I hope this isn't totally irrelevant I think the ABF would be a wiser choice with regards to the 'Rod Ratio - Kinematics' link and as mentioned by yourself: "taller block + longer rod = less stress and easier revving", which is pretty much it, in laymans terms.. From how I've interpreted it, it would seem that a longer rod is better for sustaining higher rpms due to the acceleration of the piston being lower thus less wear and frictional losses as mentioned, with a smoother flow? A shorter rod on the other hand will increase the acceleration of the piston ("but only at TDC. At BDC, the piston acceleration is actually reduced by a shorter rod (at least initially)"), thus, increased wear due to the possibility of more sideways movement with a less smooth, perpetual movement (on a very small scale)? Wouldn't the 9A/220 with the 144mm rod be relative, in some sense, to that of the ABF/238 and 159mm rod in terms of stroke to rod length? Could you fit a Diesel 95.5 crank into the 9A with the 159mm rods? How big would the issue of clearance be with this (piston and valve)? Are there any Clearance issues with a 95.5mm in an ABF? (2042cc) What would the C/R be? And what is the standard clearance volume of a 9A and ABF?
they both still have a 92.8mm crank, so its 92.8:144 (9A) Vs 92.8:159 (ABF) Been busy reading, VWs 2.0 Grp N engines were 92.8x82.5 and made 220bhp and 90.0x84.5 and made 260bhp.
I didn't know the cranks were the same in the 9A and ABF Those homoligation papers make for an interesting read indeed
well i've gotta say i was *very* impressed with the power delivery of the longer stroke engine so *if it was me* i'd look at 83.5mm pistons, 95.5mm crank - use std rods, decent pistons - and send them off to a machine shop for some serious lightening and balancing (the diesel crank would appear to havea bit of spare meat on it as std) then i'd be using arp rod bolts, skim the tops of the pistons so that they sit flush with the top of the block at TDC (on std ABF pistons you need to remove 1.35mm from piston tops) that would give you about 11:1 compression ratio. i ran 260 cams which gave peak power at 6500 revs, if you are looking at a higher rev limit i would go for straight 276's - remembering that you can use a vernier cambelt pulley to tweak the power graph and move peak torque/power around a bit. (Schrick 276's have the same lift as 268's - they just allow the car to produce it's peak torque at higher revs) depending on what fuelling/management you are planning on using i would expect this engine to make in the region of 195bhp@ around 7k rpm, 160+ bhp @ circa 6250rpm *personally* </dons flame suit> i would not put throttle bodies on it, but i would go for fully mapped injection - i'd use a system with throttle pot, and MAP sensor, no MAF meter and probably the inlet manifold from something like a 20vt i don't have the money to build the above engine (and even my dream engines are built to be what i would think is the best value) but if i was to build an NA 16v engine for a VW - the above is the specsheet of what i would build. (the only variable is whether i went for a Blydenstein 16v head, or got a 20v head worked to go on it)
Great Post. I agree with you 100% about the throttle bodies in terms of value for money. I don't dispute that if it's a stretch to afford them, then it's hardly worth it. They DO boost both power and torque significantly once well setup, yet you have to decide whether the boost is big enough to warrant the $$$!!! Personally, I'd saved for quite a while in order to build 'the dream' 16v road engine, so could afford the t/b's (just!!!). At first, I hated them, as the motor just felt crap, but after a few sessions on the dyno (and admittedly a lot more money), I got the gains I was looking for. If people are going to do it, make sure the motor is built by someone who's done it before (on a VW 16v, not any other car), otherwise you pay for the mechanic to learn, no matter how good they are.
thats great dex cheers h8sv8s,i know what you mean,mine was crap before it went on the rollers... thing is ive already got the carbs which i bought brand new @ 1k! i was thinking,along the lines ofomexfor the ignition side of things... would this be ok??? id like to end up with around 200 brake,with peak at around 8k if possible... so using either the 276's or 268's theres no extra work needed on the pistons. what is the lift on those? 11.5mm? cheers again to everyone
It depends a lot on the headwork for where you'll make peak power too, so make sure you don't get a muppet doing it!
duely noted m8, probably either blydenstein or a local guy ive heard about today,for the head work... any thoughts on this?
Diesel cranks eat big end bearings tho - there is a fella on the vortex who has been running them for a while, he reckons on replacing them every 10k at best.....
No way that I know of. I can't find the original thread but he was a respected engine builder type, and was on his 3rd engine with the oiler crank (not dueto them blowing up, just building new engines). It's because of the extra side load on the bearings due to the longer throw, as I remember. Still, replacing the bearings every 10k wouldn't be too much of a sacrifice to make for a beefy engine.......
mmm,thought it would be something like that... am i talking sh1t if i say i thought ,g60 bearings could be used to good effect can you get away with doing the bearings,with the head still on the block? last questions i promise cheers! neil. Edited by: riley
Oh aye, to change the big ends you just drop the sump, take out the old ones and put in the new - G60's eat them quickly enough themselves because the charger being driven off the crank puts an extra load on them. Not sure whether the G60 bearings are uprated (doubt it VERY much - not many ways to uprate a plain bearing in terms of longevity without sacrificing other more important characteristics) or would even fit. But it's a quick job, a couple of hours if you are being lazy, and all you need is a wee wiggly socket to get to the bastard sump bolts that are between the engine and box!
