BiTurbo228

Neat! How close can you get the colours to that teal colour you get in old evacuated tube digital displays? My main gripe with aftermarket gauges is how modern they look, so something that could pass for 80s is ideal...

Interesting to see the weight of the powertrain. So maybe 184kg for the engine and 'box as-is, ~3kg apiece for inlet and exhaust manifolds (give or take), 10kg flywheel(?), 4kg starter (if it's one of the gear reduction types) and maybe 7kg for the clutch. So 211kg or so all-in. Not bad going! For reference my 2.5l Triumph OHC and OD gearbox was 269.5kg, and my AJ6 4.0l and 5-speed was a whopping 324.6! both with PS pumps, and the Jag with aircon.

Yeah I think they're more about mitigating transient losses in oil pressure. Like little flutters of starvation that might not be an issue at 1500rpm but would cause havoc at 7000. I suppose it's a (comparatively) cheap bit of insurance if your race engine cost 10k to build...

I wouldn't be so concerned about the gearbox crossmember height (unless they're particularly ruthless in NZ). A lot of modern cars have ~150mm ground clearance, so raising the gearbox crossmember by 20mm should be plenty. Useful to know the crossmember's 180mm though. I've had to drop mine by 10mm of so but that's still plenty (though the rack sticks out below that...).

That's basically what Ford did for the Sierra in Group A racing. They were homologated with Weber engine management and changed to Bosch motronic in '87. In the first race of the WTCC they were disqualified for not matching homologation, but for race 2 they stuck a big 'Ford' sticker over the Bosch logo and passed

I don't know how visible this forum is in the grand scheme of NZ motoring society, but a non-standard e-throttle being picked up by tech inspection is dependant on the tech inspector knowing what the standard throttle was. Is it non-standard to the car that's not allowed, or non-standard to the engine? As the 4GR has an e-throttle as standard, could an argument be made that you're retaining the standard setup for the engine...

Wiring loom looks good so far. Making me wonder if I should do mine at some point, mainly for weight reduction! They carry around a lot of unnecessary copper... Any idea what the new one weighs compared to the old one?

I seem to remember applying valve lift via rocker ratio and it got even weirder, what with it changing over the course of their motion due to where they contact the valve moving around relative to the pivot point (both the follower and the rocker finger). I don't think it ended up changing things enough to align with the advertised specs, but I'm not sure he actually measured valve movement directly. The thread's here if people fancy a look. Edit: found the thread on rocker ratios too

There was a chappy called oldtuckunder in the Triumph world who did a fair bit of investigation of various aftermarket cams for the 2.5 OHC before he passed away. His main conclusion was that the advertised specifications of a cam (not just duration, but also the four timing numbers) didn't match anything at all on the actual cam grinds. He reckoned their main goal was to sound flashy so they sold cams, and make it so if someone went to a cam grinder and asked them to grind those specs they'd end up with scrap. Not sure if that's something peculiar to Triumph/UK cam manufacturers or whether they're all at it. His setup was pretty simple. Popped the cam on a lathe and attached a dial indicator and degree wheel, then turned the cam through its rotation and marked lift every degree or so. Not really accurate enough to reproduce a cam from (there's odd stuff that happens with where the radius of the dial indicator nose sits relative to the angle), but enough to get a decent comparison between cams. It's simple enough to do with a flat surface and vee blocks as well. I did it to demonstrate what everyone knew already: that the Rover 2600 in the SD1 was detuned with a weedy little bumpstick by comparing it to the M20B25.

That was my thought. Surely more flow at part throttle just means you have to close the throttle more to restrict the power to the level you need to cruise. Unless it promotes more efficient combustion or something like that...

Love that your 'midrange' is about 5000-8000rpm

I'd be tempted to pop an idler pulley on just to justify your hacking off of the timing mark. See, it was all planned out right from the start

Yeah a lot of people think the 155 DTM engine is a Busso and it's got nothing to do with it at all. The homologation is for a PRV (IIRC) that came in the Lancia Thema V6 via that Fiat/Saab/Lancia/Alfa joint big saloon project that gave us the 164 and the Saab 9000.

Man those are hard engines to find info about! 2MZ-FE looks pretty similar to the 5GR from what I can find out. Same bore and stroke, and the 1MZ is pretty similar to the 2GR (same stroke, similar bore, same conrod length, same bearing diameters). Makes me wonder whether they re-used a lot of the tooling/base components between the engines. I can't find the conrod length for the 2MZ anywhere online for anything further than that. If I could find compression height of the pistons I could work it out as I've got the rod length and compression height of the 1MZ (provided the deck heights are the same). If it's anything like the 5GR then it's probably got a pants rod/stroke ratio as well so might be a bit weak on power. VQ25 I can at least find conrod lengths. 5131g at 10,000rpm and 4156g at 9000rpm, compared to 5449g and 4413g for the 4GR. Slightly bigger piston, but offset by smaller stroke. Main bearings on the VQ are a little smaller so surface speed is better (9.99m/s at 10,000rpm), but big ends are bigger so likely heavier (offset a little by the shorter crank). Rod/stroke is on the high end of acceptable at 2.02. I chucked some ballpark numbers for the piston and rod weights in and if the VQ pistons are 40g heavier than the 4GR with rods the same then they come out with the same figures. So yeah, the 2MZ and VQ25 are probably a little more likely to be able to hit 10,000rpm from a bottom end perspective, but the differences are a set of forged pistons away from each other (if that, depending on how much the stockers actually weigh). If anyone's got a set knocking around then we can get a little further! I've got a decent amount of info on RB26s, but again RB20s are proving a little trickier to find info for. I've got conrod weight from the FIA historic database, but can't find stock piston weight. If you fancy measuring one I'll plug the numbers in! RB26s are an interesting one. People quite happily zing them up to their 8k rpm redline, but then there's been lots of people nuke oil pumps at 7500rpm which says crankshaft resonance to me. If you buzz through resonance quickly enough you can avoid it damaging things, which is easy enough in lower gears with boost. If you loiter around the wrong rpm for too long though then stuff starts going majorly wrong (oil pumps exploding, flywheel bolts backing out, valvetrain damage as motion is transferred through the chain/belt, timing scattering as the trigger wheel is out of sync with cylinder 6). This is much more of an issue for I6s with their long noodley cranks than it is for I4s and V6s (one of the reasons I think the 'I6s are the best engine configuration bar none' crowd need to go do some proper research). But still, 8250rpm is the 'max rated rpm' for the RB26 from Nissan and that's 2.6 tons. I've found weights for supertech pistons and stock rods for the RB20, and at the same 2.6 tons you'd be spinning 9500rpm. Shorter throw crank should be stiffer and lower inertia for resonant frequency too which is good, but I can't find anyone online talking about experiencing issues at a certain rpm that would point towards crank resonance so what rpm that occurs at is a bit of an unknown. Most high-revving I6s seem to top out around 3 tons, for what it's worth. Lower than high revving I4s and V6s, which I assume is thanks to the noodley cranks. You do get some over that on standard cranks, but you start getting comments like 'they start marking bearings' or 'oil pump exploded' which I don't really count as 'being able to rev that high'. Still, suggests the RB20 bottom end might have some headroom above 9500rpm. I've certainly seen some videos of 10k rpm racers, but you never know how stock their cranks actually are when there's been a lot of money thrown at them. Will watch the video when I get back home and see if they hint at how much work's been done.

Ah. Those are some persuasive numbers yeah, let's see how high the 4GR will rev as-is! Found a video of a 9000rpm 2GR Lotus Exige so someone's sorted the valvetrain. Interestingly, if they're using forged pistons about the same weight as the JUBU ones and rods similar to MWR's then 9000rpm is about 3.2 tons as well...