5 GT Turbo 11 years later silver bullet comes home

[Duncan Grier]

Only got a few short sessions in the garage this week and most of it was going 2 steps back before going forward.....resisting the urge to weld stuff in knowing I really need to remove underseal and check/fix/treat any rust hiding first

This along with thinking about longer term access, service of items and all the things not in the front yet got onto adding plans

Some very quick CAD but you get the idea with focus on suspension top pickup, then top wishbones along with the added tube after

 

[Duncan Grier]

So cleaned up front and spent some time fighting the servo options with no winner confirmed

Welcome any feedback, added drawing to any pics below on the front end beer up challenge. You can also see clearly the oem chassis leg I want to add strength back in also

 

[Duncan Grier]

Beef up challenge, not beer......that's for after working on the car

 

[Steve Swan]

Bias pedal box instead???

 

[Duncan Grier]

Bias pedal box instead???

Definitely an option and not ruled out Steve, as will predominantly a road car prefer to keep a servo although could go early lotus elise m/c setup that is non servo and easy fix

Found non servo setup on old race car and kit car fine but weight hardly anything

Atm the abs unit planned to use splits the F/R ratio from a vx220.....but may evolve to wanting some adjustment especially with fuel tank looking like up front

And I am certainly overthinking pedal ratio and feel mixing Renault pedal just because lol

 

[Duncan Grier]

So got some time last night having a proper play with servo challenge...

Looks like then oem GT Turbo one fits but does needs a bit cutting out....the Lotus one cant get in place without dropping rack/subframe but will be a similar issue....while a bit more shallow in that area is a touch wider so hard to know if can use still??

Then the M/C rotation is different between the 2 and length of bar to pedal

What is fixed by one is a problem on the other, using oem 5 auto pedal assembly and having oem means I could cut/ thread the longer lotus bar

Also found some potential smaller but deeper servo's which could work but assistance and pedal feel got my brain going wild

Some pics but looks a winner just need to consider implications of a cut and weld a recess

Anyone had experience with this? @Steve Swan @Turbell ??

 

[Steve Swan]

Years ago some cars had double acting servos which were smaller diameter, but longer front to back. R17 Gordini springs to mind. I don't like servos, they kill off any feeling there might have been. When racing there are plenty of high adrenaline moments, which servoed brakes would only make worse. It takes a long time to get things working properly with so many variables in the equation, pedal ratio, hydraulic ratio disc/ wheel ratio. Then there is the actual brake lining performance to take into account. Pukka aftermarket Motorsport ABS is very tricky using G sensors and wheel speed sensors to put the braking where it works best, a bit like an ATB in reverse. Ultimately it's driver choice. The tech may be worth the effort/ money if you will be on mixed surfaces ( tarmac rallying) can't see the point on circuits that you have to learn anyway.

 

[Duncan Grier]

Thanks Steve, appreciate the detailed response

Is starting to feel like make the oem servo/MC/ABS fit to suit oem brake setup or go non servo with manual adjustment

Only real issue is what I do now dictates what I do or dont do with beefing the front end up or it could be revisited further down the line

 

[Steve Swan]

I'll add..
Most of the cheap master cylinders come in 5 sizes only, 16mm, 0.625 thou. Then 17.5mm, 0.700thou. Then 19mm, 0.750thou. Then 20.6mm, 0.825 thou. Finally 25mm 1".
These are usually low quality and need seal kits regularly.
Ap racing's forged cylinders cover 14mm-25mm in 10 steps and on the occasions I have used them they have never given any issues. The 20.6 in liz's car the 25mm in my 8 and the 14mm clutch cyl in the Dauph have never been an issue, in the first case it will now be getting on for 20 years old. the one in the Dauph has been in there since 2010 and most of that time has not been used which is the kiss of death for the cheap cylinders, think I'm on my 3rd set of seals. If you are serious you know what to do.

 

[Turbell]

Bit above my paygrade @Duncan Grier , both make sense, Lotus set up if your using Lotus brake set up, 5 for packaging, pedal position would be my concern, are you moving it? Sitting lower, further back? What about loud pedal, assuming TFSI is FBW, how's that gonna match up.
I'd consider if you were to be unhappy with whatever you pick, can you change it? Perhaps incorporate a larger removable panel that's unbolted from the inside, allowing you to remove it from the foot well, as long as you have access to unplumb it in the bay, you could alter panel, remake it, it ain't ever gonna be a 5GT again, so you may as well go balls deep

 

[Duncan Grier]

Thanks @Turbell def not above you pay grade sir

Atm other than the steering rack mounting leg it technically works with all lotus bits that match brakes mated to 5 auto pedal so access works with dropping 5 subframe as previously designed. What I dont know is if the pedal ratio and/or if I cut some volume out the corner of the servo has a real impact. Not that servo replacement should be a regular thing so can be replaced without full car strip.

Got me thinking though on inside panel and a good call, wonder if I sit it 10/20mm back inside the car and shorten the bar if this solves the engine bay side fouling

Pedal is using oem audi pedal and incorporated DBW magic amd fits ok.......same as I did on my old 5 1.8 20vt conversion and trim body to suit 5 floor shape.

 

[Duncan Grier]

Another hour or so and revisit servo options concluded that @Turbell throw away suggestion on mounting further back in the car looks like a real viable one

Got on with measuring and seeing how the lotus servo fitted without pedal assembly in place, then dropped the front subframe and played about in oem position, similar fouling from my previous update using the 5 servo

So very roughly mounted pedal box on inside and bolted servo to it and looked doable....bit more messing about and got the subframe back in rough position and tried again, as per pics I think that can work and scallop on the rack mounting point and maybe cheeky small dent in servo if it come to it

Sits about 10mm back from oem position and bit of trimming could give a mm or 2 extra play. Might look at access/servicing could be larger panel that comes into the car although dropping subframe and 4 wishbone bolts no drama really

Also have some space to adjust pedal pivot point if come to it, and look to rotate the 4 holes to straighten m/c

 

[Duncan Grier]

Next step I think is mount the seat, will need to fabricate something as oem mounting points too far forward but can put something temp on for now. Getting the seat and driving position right is critical and can play with rack angle and pedal position before I commit

 

[Duncan Grier]

Oh and seems ARB mounting has worked out kind to me and should work out ok

 

[Turbell]

Boom !
Pay rise and a promotion for me!

 

[Leigh5t]

Boom !
Pay rise and a promotion for me!

Come off it! We all know that’s not how you get a promotion.

 

[Duncan Grier]

Ok so while had a few goes on the 5 since the last update most of it was 2 steps back to take a solid step forward.....

Parked the servo challenge as I think this is workable now after fitting slider to the seat and playing about with positioning

Turned focus back to front end strength - forward planning of cooling, fuel, servicing and strength again

Sooooo after many hours overthinking and considering options all the way from doing a full end custom spaceframe. Deliberated keeping 5 DNA v the full on spaceframe option (in hindsight probably should have done this) but what is there is true and works and can be a solid hybrid option. Also still be clearly a 5 GT Turbo while definitely way past a normal 5 build.

So cage extension into the front and beefing up what I have makes sense and what is going on.

 

[Duncan Grier]

Had planned to change the front legs straight but having a look at wheel travel I will need to raise the inner arch so where it is actually clears and better position to tie the suspension pickup inside turret...more to come on that

So turned focus to adding as per pics

 

[Duncan Grier]

Not moaning but was 40deg in garage earlier this week made it fun but continued fine tuning options and out with this lot.....always hiding some more rust so good to sort also cant lie took far longer than planned

 

[Duncan Grier]

With temperature a bit more palatable tonight got a few hours in with more cage turning up and got other hole cut and much measuring and getting cage insert ready. Needs more work and top prepped but you get the idea