Engine placement: down or back?

[Mos]

Hi,

While tackling the lunacy, a point of uncertainty has been reached. Should the engine be as far down as possible, compromising rearward positioning, OR should the engine be as far back as possible, compromising placement height?

Looking at the images below, comparing the height of the intake manifold against portions of the firewall (brake lines, heater outlets, timing cover/strut tower, etc), it can be clearly seen the yellow engine is a fair bit higher - this placement allowed the movement of the engine rearward substancially.
While I don't know all of the measurements I'm estimating the yellow engine could be 30mm higher with a potential 30-50mm rearward movement (estimate based on height of engine mounts and gearbox x-mem positioning).

I'm intending on shifting the white engine up and back to come up with some figures, but for the time being I'm curious if there are rules of thumb as to which one is "better" from a weight distribution and handling perspective. At the moment the front of the block on the 1UZ is approximately in the same position as the front of block of the 1G, within 5mm (in favour of the 1UZ).

Obviously down is good, and so is back. If there is no benefit due to the compromises of each option then ease of placement and any extra work required will take precedence, but if one (eg high/back) is better than the other (low/forward) then there's purpose in extra work.




(The white engine is sitting on a jack to give the crossmember clearance - on the mounts is sits another 20mm or so lower but there's not enough sump clearance).

Mos.

[ed]

id be going low as proportionally 30mm in the vertical axis is far greater difference than 30mm in the longitudinal axis - if you think thats valid enough

to truly know the answer to this, you kinda need to know where the roll centre and COG of the car currntly is, similarly, you need to know the corner weights. if you dont its all wild guess work.

personally id just go low, then get it as fdar back as you can from there.

things like gearbox x-member mounts, shifter position and tailshaft would be helping my decision i think

[Lambolica]

Are you concerned at all with how the exhaust is easiest to mount or are you really wanting the engine in the best position then perform miracles around the steering column?

The yellow one definatly looks alot higher than yours, and Alot higher than I think yours needs to be lifted to clear the sump off the crossmember. I think if you lift it 10-15mm to get the clearance and hen see how far back it can go and still have clearance to the firewall.

Cheers
Simon

[Mos]

Thanks guys.
Ed - yeah, many, many variables.... had a chat to Justin about your placement
The engine can go back maybe 5-10mm back at the current height (ie bugger all) - any further it hits sump and firewall more or less at the same time.

Simon - the picture is with the sump off the x-mem (it's on the jack), so it doesn't need to go any higher. Clearance on the firewall in this position is under 20 mm (maybe 16-18). If it was sitting on the sump the difference would've been more dramatic. The yellow one also has the mounts in the forward position and much taller isolators, so the bowl of the sump is partially above the crossmember. (Thanks again for your help yesterday )

Miracles will need to happen regardless... lifting it up means there's more height between the exhaust flange and the steering link, so it could be easier for room, just different routing. So yeah, I'm keeping it mind, but I'm not sure it will affect it greatly - it's a pain either way...

Mos.

[JustenGT8]

6 of one 1/2 dozen of the other Mos but if i couldn't do both down and back and had to make a call then i'm opposite to Ed and would go back. I think the benefits of bringing the mass as far within the steering geometry and towards the centre of the car outweights a lower COG.

My reasoning is based on a number of things....running adjustable height suspension i have noted that changes in height result in a much smaller handling difference than any change in mass forward or reward (eg battery relocation, diff swaps, engine length).

The fact that Toyota went from a low below the boot tank in the early TA22 to a higher but more central tank in the later 22 and 23 seems to support this as well?

At the end of the day though the difference won't be huge either way so go with whatever option makes the install easier.

[Norbie]

If it was me I'd mount the engine such that the crank centreline is exactly the same as the original engine - this is the very first thing I look at when doing an engine swap. Once you've got the crank in the right spot, move the engine back as far as practical.

If you change the height of the crank you get into all sorts of strife getting pinion angles correct - and yes I know you can do it if you fiddle around with mounts and angles and stuff, but it's so much easier to leave it how the Toyota engineers set it up.

But that's just me, I'm lazy.

[clubagreenie]

I thought we decided this?

Given approx same weight as 1g (?) keep position in bay same relative to No1 cyl. V config vs inline 6 should be slightly lower CoG for the engine. Either way you need to mfct exhaust and tailshaft. Clears clutch master better (in fwd pos), Gbox xmember rear holes line up with existing chassis holes. Make the list.

[Mos]

Yeah, I thought it was decided too, but I had more thoughts ...
*AND* the Rod Millen built one is also higher and further back.... but I can't, at this stage, figure out how they cleared the firewall....

The 1UZ block is approximately 500mm long with 140mm of superfluous crap in front.
The 1G block is approximately 550mm long with 140mm of superfluous crap in front.

The back of the gearbox has moved forward 50mm, so it can be concluded the front of the block (and engine) is at the same position, so the COG of the 1UZ is actually forward compared to the COG of the 1G... which implies bad. (If we make the assumption that the COG is in the middle of the block, or slightly forward of the middle of the block, longitudonally speaking).

Now as to the height of the COG within the engine, I would expect the COG of the 1G to be significantly higher above the crank than the COG of the 1UZ.

So.. with the assumptions made, currently the COG of the 1UZ will be lower and forward wrt to COG of 1G. The implication is that moving the 1UZ up and rearwards would move the COG backwards (possibly past the COG of the 1G) and upwards (hopefully still below the COG of the 1G...). The summary conclusion would be that the COG of the 1UZ will be better, or no worse, placed than the COG of the 1G (in both axes) if it moved up and back.

Does that sounds like a bucket of poopoo?

Justen - cool, thanks point taken The only way I could do both is with significant modifications to either the sump or the crossmember, either of which I'd prefer not to have to do....

Norbie - I have no idea where the centreline of the original crank is anymore (I'd rather not put the 1G back in as I may be tempted to just put everything back together )

Mos.

[ed]

is the gearbox offset measured with a w58 with my bellhousing installed?

[Draven]

dry sump ftw! (of course, everyone has an unlimited budget to do this).

Based on common sense and no scientific validation whatsoever, I'd be pushing the engine back as far as possible, and not be overly concerned about the CoG... of course in the real world, the 40mm or so we're talking about here will most likely make precisely buggerall difference

[river]

Hi,

Norbie - I have no idea where the centreline of the original crank is anymore (I'd rather not put the 1G back in as I may be tempted to just put everything back together )

Is this the IS200? If so, are there not other IS200 owners here that can tell you that?

seeyuzz
river

[Mos]

Ed - measure with the 5 speed auto, which is the same length as the 4 speed off the 1G.
The W58, with the 1UZ bellhousing, and the current shifter arrangement, would poke straight through the centreline of the auto shifter (and need about 100mm of tailshaft lengthening).

Greg - The real reason for this thread is procrastination Although I'd like to do it once, and only once, and have no regrets about it. If it handles worse I'll be pissed.

River - yeah, there are, and I have photos as well. With the radiator and undertrays it's hard to get in there but yeah, it's possible.

Mos.

[clubagreenie]

of course in the real world, the 40mm or so we're talking about here will most likely make precisely buggerall difference

Thats was my thinking, just go for the option that has the least hassles assosiated with it, being the fwd IMO. The engine goes fwd but gbox goes back with longer bellhousing.

[Draven]

I understand Mos - the 1s200 has very nice dynamics from the factory. you don't want to spend hundreds of hours and thousands of dollars to end up with a worse handling car than you started with
It really does make me feel like I'm cheating using "bolt-on" mods... oh to have the time and money to do another real modification

[Billzilla]

If you're only talking 30mm here or there, you're really not going to notice much difference no matter where you put it.
But given the choice, go low, as it'll likely make getting to the oil filter and making the extractors a little easier than pushing the engine back as far as possible.

* This reminds me, I should write a short technical artical on how to build a cheap dry-sump system. People who don't know pay far too much for them and they shouldn't.