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[markrnorton]

you have done a fair bit of work there. The throttle body over bore looks nice work, do you think it will yield much power ? or just smooth things out a bit

All i have done on my project is the front suspension !
Sloow this building malarkey

[lozzzzzz]

It certainly is slow, I've been at it for 2 years now I can't wait to drive it again, in fact its probably taking so long cos I keep sitting in it imagining what it'll feel like to drive it again (and maybe making brum brum noises ).

The TB should increase air flow at high RPM when the engine is swallowing the most air, the throttle body mod on its own won't make a difference untill a fairly high figure. Its a shame I couldn't do a before and after test run, but rolling road time is so expensive. 

[markrnorton]

its a shame there isnt a bigger twin throttle body available. I suppose one could be made up or even grafted on from another car.

not sure it would be worth it, unless going full out on an engine or forced induction.

[lozzzzzz]

I had thought about grafting another one on, the boring out was the easy part so my thought was to bore out the body and mount it with no internals then mount a bigger body with a hose between it and the original TB housing, but the original is still the greatest restriction so I though I might as well go the whole way and do the butterflies too. 

When grinding out the TB mounts in the plenum, it was apparent that it couldn't be ground out too much bigger, so to really upgrade the front of the plenum would require major work.  But there isn't too much point in this with the thought of force feeding the engine in the future. 

[markrnorton]

It does appear the main restiction is the TB's and mounting point on the plenum
When the time comes i may play around with individual TB's, maybe from a Truimph MC (3pot)

[Kevin Wood]

When talking about the "main restriction" don't forget to include the whole system from air filter to exhaust tailpipe. 

Do we know that the throttle body is a significant restriction already? I think the next thing I'd do is a back to back dyno pull with a standard throttle body and a bored out one just to ensure that the weakest link is not elsewhere (valves, cams, head ports, etc.). If it is, further throttle body work is a waste of time.

Manufacturers will rarely specify a component like a throttle body undersize so it'll significantly strangle an engine. That said, they won't make it larger than required either, to keep intake velocity up.

ITBs would certainly be a good move if NA tuning for power. If keeping the low down grunt and flexibility of the engine is a priority I'd stay with the standard setup until it's been proved to be holding it back.

Oh, and I've heard an X30XE individual throttle bodies. That might be a deciding factor, actually.

[markrnorton]

When talking about the "main restriction" don't forget to include the whole system from air filter to exhaust tailpipe. 

Do we know that the throttle body is a significant restriction already? I think the next thing I'd do is a back to back dyno pull with a standard throttle body and a bored out one just to ensure that the weakest link is not elsewhere (valves, cams, head ports, etc.). If it is, further throttle body work is a waste of time.

Manufacturers will rarely specify a component like a throttle body undersize so it'll significantly strangle an engine. That said, they won't make it larger than required either, to keep intake velocity up.

ITBs would certainly be a good move if NA tuning for power. If keeping the low down grunt and flexibility of the engine is a priority I'd stay with the standard setup until it's been proved to be holding it back.

Oh, and I've heard an X30XE individual throttle bodies. That might be a deciding factor, actually.

I have used overbored TB's before, they do make a small difference, but it has to be taken in context as you say, the whole intake/exhaust system.

The thing i have found over the years is you have to put the effort in if you are looking for the additional power, however small the gains. But a small bit here, a small bit there soon adds up.

I do think that individual TB's would make a significant difference in power and its delivery , if sized correctly.

[Kevin Wood]

I have used overbored TB's before, they do make a small difference, but it has to be taken in context as you say, the whole intake/exhaust system.

The thing i have found over the years is you have to put the effort in if you are looking for the additional power, however small the gains. But a small bit here, a small bit there soon adds up.

This is what modern engine design and the need for efficiency and emissions has given us IMHO. Production engines are engineered in such a way that there is no longer one weak link that, when eliminated, gives us another 20BHP, as might have been the case with older engine designs.

Everything in a modern engine now has to be sized for the target power output, and it therefore follows that, to get a significant increase by conventional tuning, you will need to tweak most parts of the engine (or go forced induction).

I do think that individual TB's would make a significant difference in power and its delivery , if sized correctly.

Yes, but you will struggle to get a long enough intake tract for them to work well at low revs, so probably worth considering about the same time as cam upgrades, where you'll be sacrificing that anyway, IMHO.

[markrnorton]

I have used overbored TB's before, they do make a small difference, but it has to be taken in context as you say, the whole intake/exhaust system.

The thing i have found over the years is you have to put the effort in if you are looking for the additional power, however small the gains. But a small bit here, a small bit there soon adds up.

This is what modern engine design and the need for efficiency and emissions has given us IMHO. Production engines are engineered in such a way that there is no longer one weak link that, when eliminated, gives us another 20BHP, as might have been the case with older engine designs.

Everything in a modern engine now has to be sized for the target power output, and it therefore follows that, to get a significant increase by conventional tuning, you will need to tweak most parts of the engine (or go forced induction).

I do think that individual TB's would make a significant difference in power and its delivery , if sized correctly.

Yes, but you will struggle to get a long enough intake tract for them to work well at low revs, so probably worth considering about the same time as cam upgrades, where you'll be sacrificing that anyway, IMHO.

I have a fair amount of space/clearance under the bonnet of the kit, so might get a compromise on intake length. Low revs/torque isnt so much of an issue either with the lack of weight. However it needs to be tractable/drivable 

[Kevin Wood]

I have a fair amount of space/clearance under the bonnet of the kit, so might get a compromise on intake length. Low revs/torque isnt so much of an issue either with the lack of weight. However it needs to be tractable/drivable 

Indeed. not an issue in a light car. My westfield has comparatively little below 3K RPM yet will happily keep up with traffic in 4th. Only mechanical sympathy causes me to change down. If you are "pressing on" you're keeping it above that speed, where it takes off like a thing possessed, so no issue then either. 

In fact, having a lump that doesn't dole out loads of grunt at low revs makes it less likely that you (or SWMBO, if you're on the way back from the pub) will get yourself in trouble  at the expense of little loss in  performance, IMHO.

[lozzzzzz]

I'd really like to do a back to back comparison I'll dispell the myths   First I need another throttle body as the one Ihad on the engine I'd already fettled with the die grinder ( can't leave anything alone.

An update...

There is lots still to do on the scimitar, but three major jobs remain, the roll hoop needs making (toying with the idea of having that done else where), the diff needs putting in and the rer caliper mounts need making.  I tried to tackle the diff at work but we couldn't get the bearings off.  This weekend I went to visit an old uni buddy of supra powered capri fame) with a good bearing puller and a height measuring thing and I've nearly ticked diff off that list.  Well the difficult part of the job anyway. 

First of all I had to make the extension for the height vernier (i'm not actually sure of its name but this seams like a good name).  It has to be quite rigid to give repeatable results.  I also drilled a hole to mount a dial guage to it as this job requires a lot of accuracy (you only find zero on the dial guage then measure from the height vernier). 


Next the flat glass surface was read off as the zero point (turned out it was easily manipulated so that it was exactly 2.5" up the scale), so this value could be sutracted from all the measurements taken.  The the original diff measured with its bearings still on.  The base up to the CW mount face was measured and the total height from bearing to bearing was measured. 


I brought along two open diffs (to choose the best bearings from the set) the quaife and pete also had his open diff about with his powerlock out for a change of CWP, so we had for 5 4HA diffs on the side at one point


Next the Quiafe was measured a millioin times to make sure I was getting it right and it was repeatable, the a load of head scratching and calculations were done, the right thickness of shims put on and the bearing tapped into place, this is the half way point.  Then the top bearing was measured to find exactly the thickness of shims needed for the top bearing.


And the final assembly I measured and measured and there was no measurable difference between this and the original diff measurements


TheQuaife neeeded lots of shims on the bottom (over 4mm), and very few on the top, the bearing stub actually sticks out of the top bearing a little so I have to lathe it back a little before it goes in, but I'm really pleased that this job is ticked off. 

More to come

[markrnorton]

is the Quaife diff the ATB type ?

[lozzzzzz]

When I got home and tried it in the axle (without the cw on) it didn't turn entirely freely which concerned me slightly.


But then I didn't try this with the original diff.  With the CW on and the diff back in place, turning the pinion flange seemed to be just as before.   I took a torque wrench reading off one of the CW bolts measuring the torque necessary to turn the diff and pinion from this point (4ft/lb), I'm waiting for my buddy to set his up correctly just to check mine is in the right ball park. 

It was good to see his axle apart again, we set it up a couple of years back and its been taking a hammering from his 400hp supra turbo engine, and the great news is that everything looked spot on, we assemble it in a bit of a hap hazard way (we've certainly been more careful and accurate this time round with his and mine), so its good to see it standing up to all that torque to well, especially the little spacer in the middle of the diff separating the half shafts. 

On that subject, I've taken the diff out and set about measuring up for the half shaft separator that quaife supplied.  There's not a lot to see really but I'll explain.  you're meant to take an end float measurement from one of the drive flanges and its meant to have 0.15-0.2mm of free movement.  In the past I've found this very difficult to measure accurately.  So instead I've put the half shafts in with the diff out and used feeler gauges to measure the gap between the half shafts.  You can see the little spacer in the middle.



With all the shims removed there was still a gap of 0.65,  So I put the bearing retainer on the lathe and took off 0.5mm of material leaving a raised section that would push the bearing slight further into the axle casing and close up that gap. 



A lot of fettling later and its now got the 0.15mm gap leaving a little tolerance for the new part wearing in. 

Oh and to add tot he job I found that the bearing surface on the inner end of the left half shaft had a lot of wear with small chunks of the surface completely missing, luckily I had a spare lying around with a better surface, I think this is pretty important with the center spacer being so much smaller than the original. 

I dug up the old rear brake conversion thread and now have another set of new (i.e. not leather) axle seals on the way.

More to come

[lozzzzzz]

Had an afternoon on the car on the Sunday, the axle is pretty much ready to go back together now, the new seals have arrived, but I'm still waiting to hear from my buddy about how hard it is to turn his diff. 

So I took a very long time about making the lower switch panel thingy to house the extra switches.  I've put two accessory sockets in as I had both lying around and I thought the laptop might spend some time in the car.  The lower switches are for the fuel pumps the upper one is for the engine fan (the ECU operates it, but its nice to have an override) and the push button is to silence the buzzer. 





As you can see I added another strip of ali lower down to fill the gap left with the rest of the center consul missing. 

The Mechless stereo has arrive and some small speaker boxes, there is a phone mount on the way to finish the center dash and a wideband lambda gauge to go in place of the clock. 

More to come

[markrnorton]

Nice bit of work. The gearlever sits nice on the tunnel, looks like it was meant to be there