BiTurbo228

Yeah a lot of the issues with the I6s will be something to do with torsional vibrations, which the V6s will be much more resistant to. Even though the crankpins are shared, they're so much more compact than the long noodly cranks of I6s. Judging by Roman's picture the GR crank has proper flying arms between adjacent crankpins rather than the sketchy offset-ground pins of things like old Buicks, so that should help a lot with stiffness too. I was half thinking about torsional issues and half thinking about pressure on the oil film between big end bearings. All exciting stuff we get to find out about

It'd be interesting to know what length the 2MZFE rods are. I've got the 5GR rods at 154.38mm which is the odd one out of the GR family. Not sure what that does to your piston compatibility. There's a few estimates and fudges in my calcs, and they're for a 2GR with various different crank lengths, but dropping to a 69.2mm crank from a 77mm crank shaves about 350kg off the peak weight exerted upon the crankpin at 10,000rpm (assuming forged pistons and rods). That's down from 3397kg peak to 3056kg. For reference your 1NZ was at about 1702kg at 9000rpm with forged internals, but it did have a weedy little crank. 2JZs start to show increased wear rates above about 2700-2800kg, but will run to 3000-3250kg if you don't mind about that. BMW S54s are at about 3350kg at 8000rpm, though they have semi-complex issues around bearing failures that no-one's found a definitive cause for (some fail at 8000rpm, but there's enduro cars running 8200rpm and ~3500kg with no issues). RB26s start experiencing issues between 7600rpm/2100kg and 8750rpm/2800kg, but it's oil pumps that they grenade so that's probably torsional vibrations. KPR's short-rod 4AGE at 10,000rpm is a smidge under 3000kg. Who knows whether these limits are anything to do with peak crankpin loads or not, but it's good to see that at least 10,000rpm on a short-stroke GR doesn't seem wildly out of the realms of these other high rpm engines.

3GR heads would offer benefits in much bigger valves. Probably not worth getting one for these teething stages, but as an evolution it would be neat.

Just caught this one, love a good Scimitar. Especially the SE5s.

I bought an alloy rad from the States that was a really nice design (good thick cores), but sprung a leak where the fins joined the end tanks. Then bought a cheapy eBay special alloy rad (not actually all that cheap) which has thinner cores, but seems to have held up. Probably just unlucky...

Don't I know it! £300 a pop...

I feel like I've got some shims somewhere, but I'd need to find them...and then post them from the UK anyway. TBH it's the finding that will probably take the time...

Maybe what you need is two basic bike mufflers The stock SD1 exhaust has a swan pipe tip and if you stick a straight one on that pulls fumes into the cabin. Maybe a side exit might help, even if it's not a full swan neck. I've got proper side pipes on my SD1 and it's fine while driving along. Does steadily gas you when you're stationary though...

Well, that sounds like a saga and a half! Always the way when you're working to a tight deadline, though I must admit I haven't had the whole 'bitten by a cat I was trying to help' thing happen to me specifically... Sounds good though. Sounds real good.

Probably smarter. I just took one look at the price of remanufactured master cylinders or my Mk1 and thought 'screw that for a game of soldiers'. Been thinking of trying to do a servo-into-twin-masters things somehow as that'd open up opportunities to do something similar with my SD1, but not got that sussed yet.

Not sure what your engineering stuff would say about it, but I've made a twin master setup to work with mine. Cut out the middleman of a pendulum box and just made a plate that bolts to the bulkhead: A T2000 might be on the upper limit of what I'd want to drive on the street with manual brakes, but hopefully it'll be fine!

No mine was fine interestingly enough, though I did end up doubling up on the copper washers as my helicoiling wasn't as straight as I'd have liked it (did it on the car which was a fun experience...). I think I did give it a bit of a light blocking down to take off any high spots and raise any gouges that might make sealing trickier.

Yeah I've got a straight plug with a copper washer in mine. The tapered one mashed the threads before it sealed and I had to helicoil it.

Yeah maddening. Checked for shaft vibration on all your auxiliaries?

Glad the bottom end's fine. I read on Guy Croft's site a while ago that sometimes the turbo blocks can develop a warp that robs power, possibly due to a manufacturing defect as it seems to be random. Not sure if it affects other blocks, but if the crank spins freely it's probably not that. What are the rings like on the pistons? Any of those caked up? I remember when I rebuilt my Triumph engine the first time I forgot to clean out the ring gaps and it was very stiff to turn in patches.

At least you're not charging someone half their paycheck to show them how...before you've managed it yourself. That's a future business venture $99/month - how to modify your block with a cordless drill $1999/month - how to splooge together ITBs using a 3D printer and CF I'll leave the production tier options up to you

$2000 a month for an exhaust that doesn't sound like the guy was intending it to? Think I'll pass...

An alloy block alone won't save you. That Jag AJ6 I have is all alloy. Though it would be truly gargantuan if it wasn't... Very true on accessories. Plenty of 10kg alternators and power steering pumps out there, not to mention AC pumps. Gearboxes are another killer. The LT77 would probably weigh 10kg less if it had an alloy centre case, and 6-speeds are generally 5-10kg heavier than their 5sp counterparts. Flywheels are another major point of variance. Could be a nice little 8kg solid thing, or a 22kg dual mass. Oh, is the starter included in your weight?

209kg all-up including gearbox is very impressive. Doubly so considering the block is big enough to stretch to 3.5l at least. Some other combos I've seen (as in, actually seen pictures of them on scales so I can tell what's included or not). Rover V8 3.5l carb and LT77: 221kg (not helped by 50kg gearbox, also not including headers as I haven't dug those out to weigh yet) BMW N52 and GS637BZ: 218.6kg BMW S54B32 and G420: 283kg Mazda 13B Renesis and 6-sp: 204kg Subaru FA20 and 6sp: 218kg My honker of a Jaguar I6 and G290: 325kg Also, could not be more accurate on the lack of garage space. Certainly feels like purgatory.

Can recommend A539s. Had them on my X1/9 and they did everything I'd expect a tyre to do, wet or dry.

Nice work on the axle links. Land Rover Discoveries have something similar in their axle location, with a single upper a-frame providing both fore-aft and side-to-side location. Theirs also houses a central gas strut for self-levelling which I thought was clever.

...and port graph. Discovered a few more caveats. I know for certain that the ST205 and Duratec have been measured on a diagonal. Most of them are nice and give you a true cross-section, but some don't and others are ambiguous (i.e. just give you a shape with no accompanying port diagram to indicate where it's taken). Others specify a port measurement a certain distance down the port (ST185 compared to ST165 is an example, as is the Delta Integrale, Maserati 24v and the Dolly Sprint). I suppose take this graph with a real pinch of salt as the data is much more suspect than the valve graph at the moment.

Right, double-checked all the data for accuracy, plus added in as many more as I can be bothered with on the FIA site. Up to 116 multivalve engines which is a respectable(ish) number. Only done the valve size chart so far, because if you want to know what true MS Excel pain feels like you're free to try getting all the data labels legible on a graph like this: Some interesting things that struck me, mainly at the lower end of the chart. I know Saab B204s are capable of well over 200hp/l without changing the valves (1hp/cc!), despite the fact that they look woefully undersized (especially on the 2.3l). Maserati valves do look very small like we expected, but maybe that's not so much of an impediment if you can just ram boost into them. Also, TU5J4s are also capable of well over 100hp/l (as is the FJ24 240RS), again despite what look like relatively small valves. I suppose we could conclude that anything that's not at the complete extremes should work well enough, and even extremely small valves are secondary to other concerns in boosted engines (possibly provided the heads flow well despite the valves). Very few, if any, of these engines are 'poor performing'. I haven't done a 2v chart yet, so it could well be that '99% of multivalve engines have enough valve area to make power' might be a better conclusion (though the Maseratis and Saabs are getting there at bigger displacements). Oh, and to keep this on topic for a 4GR. Still looks like you won't be wanting for valve area for revs. Ports next. Wish me luck...

@Roman You wait until you get into valve-to-port sizing. It's a more reliable measure on 2v engines, but those vary wildly in approach. Seems to be a fair few close to the 'ideal' ratio, and another big chunk going down a 'small port, massive valve' route, and a handful with monster ports for a tiny valve (like port openings bigger than the valve diameter). Some of the Homologation docs have some pretty detailed info on cam specs as well, but that would be a total bear to transcribe. I was wondering if some of the 'huge valve compared to port' engines were making up for mild cam specs by oversizing the valve. I suspect this is the case with my Rover 2600 engines. Super-needly cams with very little low-lift, but big valve compared to port so that small low lift translates to an adequate curtain area increase. Really what you'd want to do is plot port geometry (including minimum area) and valve size against valve lift, cylinder volume and BMEP...controlling for all of the extraneous variables like fuelling, ignition, weird intakes, cultural trends and anything else you can think of. But at that point you're getting into producing your own engine model, and I'm rather hoping my back gets better before I get that bored also, would probably take less time and effort to make the money to build 3 different engines of the one you want and test them... Iterative empirical testing of the actual engine you're going to use is really the only sure-fire way. If you're lucky you've got someone like Vizard or @kpr who's done it for you and published the results. If not, that's where I was trying to get some kind of steer with the graphs so at least you can start with a semi-informed hunch (when added to all the empirical data of other engines that may or may not be applicable). @Truenotch Thanks! And yeah sure. I've added in the earlier 3S-GE from an ST165 and it's up there with the big port, big valves Japanese crew (4.06mm2/cc ports, 3.53mm2/cc valves). Doesn't appear to have data on the later engines, so if you've got some calipers and a spare head that'd be dead useful! As both @kpr and @Roman mention the FIA dimensions for port sizes can be misleading. I suspect what actually matters is the size of each valve's individual port past the split, but the FIA papers only state the dimensions at the cylinderhead face. Some engines are nice and have individual ports for each valve so you can get a better steer. I wonder how many early-ish 4v engines with huge ports are actually much smaller when you account for the actual port size. I've got a fair bit of googling ahead of me I suspect to try and find that info out for as many engines as I can. Even if I can't find someone who's actually measured it, I could fudge something to get closer by taking the outer radius of a flattened oval port as indicative of the ports after the merger. Not even close to perfect, but probably closer. @fuzzy-hair-man Useful to know! There's a fair few engines like that, that are obviously optimised for smaller displacements and have compromises when you slap them on bigger engines. We seem to think the Maserati 24v head is like that. It seems to be midrange when you put it on a 2.0l engine...but they also fitted the exact same head to a 2.8l. Oh, and as a general comment I've been going through and cleaning up some of the data a bit. Not many big errors like the RB20, but getting a more refined area from the specified dimensions. Probably a little premature making graphs from it, but I was over-excited

Yeah I'd definitely buy that as a development trajectory, with the differing engines in the charts at different stages along it. You can certainly plot that trajectory through Japanese engines from things like the 20R with its teeny tiny ports, through the 5M with more generous ports to the 7M with massive ones. Need to get some good data on European engines of the 'Medium EFI and VVT eras' as I've only really got a handful of them to check against, and none are particularly up at the pointy end of port sizes (aside from the Volvo 20v anomaly and the Alfa 3.0l 24v). American and Ozzy engines tend to be poorly attested in the FIA record though, so there's limits there as well. The exhaust scavenging idea would make a lot of sense as to why I see totally junk manifolds on BMW M inline 6s where a good 6-3-1 on a dodgy old Triumph OHV is utterly transformative. Always seemed like power and torque left on the table to me, but perhaps not. Absolutely agreed that there aren't any hard and fast rules, and trying to apply averaged rules of thumb to engines is a bit of a fools game if you're not experienced enough to know what's what. Hence why I was trying to get a bit of a database going. That way you could look at your head (in my case a Rover 2600 that precisely one person has ever done anything with), look through the database for a couple of other engines with comparable design parameters, and maybe get a bit of a steer about what to do. Less 'become an expert tuner overnight through data crunching', more of 'try to get your first stab in the dark roughly in the right direction with an unknown head'.