Prawn and BigAls A3 Track Car

[Stuart B]

every time I see a new post on here - I expect to see something fast and you are showing things to make you slower

 

[hydro s3]

They look amazing. The car will look good with them.

 

[Rainbird]

Yea, it is

Once you go black.....

You go deaf?

 

[nightroamer]

Those look pant soilingly good


Sent from my iPhone using Tapatalk

 

[sparrow]

 

[Erikn89nl]

You go deaf?

I thought, "you need a wheelchair"...

 

[Prawn]

I've got no brakes!

Bye bye cp5200 setup!
What utterly brilliant brakes these have been.

Can't wait for the next chapter!

 

[bigal 1]

I believe the next chapter is going to be interesting. Read that as frightening performance when all mods completed. I'll have to go to Specsavers to be able to read the upcoming speed of the tarmac. This of course is concerning me .

 

[antwan64og]

Don't worry Al, it will probably only reach a real 175mph.....

 

[Prawn]

Don't worry Al, it will probably only reach a real 175mph.....

That's a fairly terrifying thought isn't it

I've never been into top speed runs really, but if other videos floating around from various cars Bill has mapped are anything to go by, its going to get to 150ish insanely fast, then just keep going!

 

[bigal 1]

175 mph, that's ok. Where do you reckon that would be then, Donny or Coombe or maybe back straight at Bedford.!!!

 

[antwan64og]

With a 7500rpm rev limit, plate diff 02m and over 400hp at the wheels i'm sure it will be "entertaining"!

My prediction for the end of 2018 is SQS 6 syncro kit (boost) and SEQSHIFT, sorry i just spent another £3k of your money in my head, lol

 

[Prawn]

175 mph, that's ok. Where do you reckon that would be then, Donny or Coombe or maybe back straight at Bedford.!!!

More likely on the Basingstoke Ring road than any of them

With a 7500rpm rev limit, plate diff 02m and over 400hp at the wheels i'm sure it will be "entertaining"!

My prediction for the end of 2018 is SQS 6 syncro kit (boost) and SEQSHIFT, sorry i just spent another £3k of your money in my head, lol

Rev limit will be 8k ish was always 7600 before. I'd go a little higher, but it won't be making power that high without cams so no point.

I ****** hope it doesn't end up with a full gear set! The money spent this year is absolutely obscene even after some pretty extensive wheeler dealering on my part. For 2018 I'd really like to see it 'finished' in it's planned state, and then enjoyed without too much work in terms of alterations, just routine maintenance and fixing anything which may break. Eek.

 

[antwan64og]

just routine maintenance and fixing anything which may break. Eek.

Why do you think I said the cheapest strengthened gearssets I could find, lol.

I kid, i kid.

It's going to be epic no doubt

 

[sparrow]

I ****** hope it doesn't end up with a full gear set!

I used my dog box in anger for the first time at Donington. The difference is night and day, upshifts are so much quicker and smoother.
Downshifts require more finesse with rev matching required, which I was a long way from.

 

[bigal 1]

I've been on that ring road when you were testing new tyres. For legal reasons I can't say any more.

 

[Prawn]

So, life is very slowly calming down a tad, and in the last few days I've managed to get 1 or 2 short trips out to the garage!

First up was sorting out the things I've sold recently. People have been incredibly patient with me waiting to get bits off, so that was first to get sorted out before doing any more work.

The AP brakes were removed, cleaned up, boxed up, and have now been sent to their new owner, who will hopefully be very happy with them

I'm also sad to say that I've sold my OZ SuperTourismo wheels. As much as I loved them, they're not going to fit over the new brakes, so they became of zero use to me overnight! These have been sold to fund the bells and brackets for the new brakes, so it's not all bad!

Not sure if I posted this before, but I really wasn't happy with how my gear cables sat in relation to the wastegate pipe:

Mark has modified the manifold previously to stop creep, but unfortunately this created more issues with gear cable placement. On his car they just about cleared as his cables come through lower with his shifter under the car, but despite moving the cables to different locations through the bulkhead I just couldn't make it clear.

With the manifold wrapped, and everything fitted and in the car, I wasn't about to pull the manifold to have it altered at this stage, so I decided so make up a short extension to move the wastegate across.

The only issue was, whilst the manifold flange is very easily bought for people making their own, getting hold of a flange that replicated the Tial gate to make the extension seemed impossible!



As pure luck had it, it turned out that the ebay 2" stainless v bands I already had wern't that far off!

Here's the one that's similar to the Tial:

And here's the other one on the Tial housing to show how it sits:

As you can see, the OD is slightly larger, and the angle on the back that clamps up is slightly different.

Thankfully, Andy has a lathe!

First up we took some material off the face of the female flange, to make sure the recessed seat was the same 1.5mm depth as my manifold, reduced from 2mm. This ensures that the Tial valve seat will be tensioned correctly when it's all tightened up.

Next up we reduced the OD on both flanges:

Then we recut the angle on the back of the flanges to match the Tial flanges and clamps:

First one done, offered up against an unmodified one to show the change:

And lastly, the protruding lip on the male flange needed reducing in both height and diameter:

This now replicates the wastegate and sits perfectly in the manifold fitting:

And the plan to put all this to use:

a short extension with a slight crank. this moves the gate well clear of the gear cables and positions the outlet nicely for it's exit into the tunnel

 

[Prawn]

So, with a wastegate in a position to link back into a downpipe, I guess I needed a downpipe!

I started with the 4" elbow section that Mark had made. This seemed pretty decent, and I wanted to keep it, so I cleaned it up with a flap wheel, and cut off the existing v band on it as it didn't match the ones I'd bought.

I shortened the lower leg by about 50mm too, to gain more room as it goes into the tunnel, then tacked on a new v-band to start my adventures with exhaust fabrication!

From here I needed a small bend to take be towards the centre of the tunnel:

Before then kinking the other way to start to exit the tunnel:

I've used only large radius bends on this. I have some tight radius bends, but I wanted to avoid using them as the more open the bends are the better it'll flow, and and we all know, it's all about the flow™.

After this point, I could have just angled the outlet towards the tunnel and come straight down, but I wasn't happy with how it would sit close to the steering rack. I wanted to maximise space above the rack to avoid heat transfer to the steering fluid, and also keep it as far from the tunnel as possible to avoid knocking.

Here we see it exiting nice and central:

I decided to put a little hump in it across the rack, again using sections from large radius bends. All cuts to all pipes have been cut square. I know some people use them a lot, but I absolutely HATE pie cuts. I just don't see how they can flow as well.

Next up I removed the old centre section, and cut out the old redundant centre box. Regular readers will remember that this rotted away inside a few years ago so I cut the internals out and it was just an open chamber, so I think this was best removed.

I've added a v band at the back of the tunnel now, so the whole centre section is easily removed, or replaced with a cat section for 'road use'

All that's left is to fill this gap. This will contain the main flexi for the downpipe, and a final V band connection for the removable centre section.

Slow progress as usual these days, but it's all slowly coming together!

 

[<tuffty/>]

Welding tape (tm)

<tuffty/>

 

[sparrow]

Nick, what silencer are you using? As your set up is pretty similair to mine, I think it's worth pointing out now that I have a single small silencer at the back, and was 103dB at Donington, so will have to add a (very large) center silencer.

 

[<tuffty/>]

Nick, what silencer are you using? As your set up is pretty similair to mine, I think it's worth pointing out now that I have a single small silencer at the back, and was 103dB at Donington, so will have to add a (very large) center silencer.

You still planning to go back to quattro? this will dictate the silencer to a degree...

quattro rear silencer setup is different to FWD...

My exhaust is quiet

<tuffty/>

 

[sparrow]

You still planning to go back to quattro? this will dictate the silencer to a degree...

quattro rear silencer setup is different to FWD...

My exhaust is quiet

<tuffty/>

Eventually, yes. However, as I want to develop the car first, and make it reliably fast, I'll need a few track days, so a big silencer will need be fitted. Even more so as Donington and Bedford are the two closest tracks to me....

 

[antwan64og]

My exhaust is quiet

<tuffty/>

Is it actually quiet? Even at WOT only slightly louder than stock?
Or just not ear bleedingly loud?

 

[<tuffty/>]

Eventually, yes. However, as I want to develop the car first, and make it reliably fast, I'll need a few track days, so a big silencer will need be fitted. Even more so as Donington and Bedford are the two closest tracks to me....

Fit a bigger one at the back... saves doing the job twice

<tuffty/>

 

[<tuffty/>]

Is it actually quiet? Even at WOT only slightly louder than stock?
Or just not ear bleedingly loud?

Never gonna be 'slightly' louder than stock at these power levels with a full 3" straight through but it doesn't drone in the car and while on WOT it gets louder its not race car loud..

Pretty sure Bill has a Db 'o' meter at the workshop so if I remember I'll do a static 5000 rpm or so test...

<tuffty/>

 

[Prawn]

This is my rear box Alex, shown here next to a fwd miltek box for comparison:

It used to have a small centre resonator in:

With the resonator, it used to be between 88 and 92db when tested.

About 18 months ago the perforated centre of the resonator rusted out and started rattling inside the box, so I cut the resonator open, removed the contents, and welded it back up as a random chamber in the exhaust.

After that it used to test at between 92 and 94db, so amazingly still not that loud!

I'l be really interested to see how loud it is with the new turbo and fully straight through centre though. In theory the straight centre shouldn't make any difference, but I reckon the tubular manifold and proper sized turbo will be a lot more 'open' and make it a fair bit louder!

I've spent quite a long time getting the centre section to sit dead central in the tunnel, so I should have room for a 24x5" massive centre silencer if I need to tone the noise down loads. The mid pipe has v bands at each end for that very reason too

I guess I need to hurry up and finish it if I ever want to know what it sounds like!

 

[Prawn]

Just realised I never added a pic of the downpipe as it was before I started the wastegate work:

First job on Sunday was to connect the downpipe to the rest of the exhaust. This looks every so slightly off straight here, but it's not all aligned and tightened up in this pic, just sitting in place for the photo:

Moving onto the wastegate pipe, I did some measuring up, and worked out the angle I wanted to approach the downpipe at:

I then worked out the angle this would join the downpipe, and set about making a profiled tube to meet the downpipe:

I then tacked this into place to check fitment, and removed it all and added a V band as the downpipe wouldn't come out as a whole piece:

With everything checked and fitting really nicely, I cut the spot welds off the main downpipe connection to make the hole through to the exhaust:

Holes drilled:

And opened up to break through as many as poss:

And snipped out with tin snips:

This was then smoothed out with the awesome little power file that Dad bought me for Christmas last year.

More pics later tonight when I'll hopefully get it all finished and ready to send to @Lavis89 who's very kindly offered to TIG it all up

 

[Stuart B]

Question?
Is the waste-gate to downpipe pipe ever going to get exhaust being blown up to the waste gate through back pressure? or is there some sort of flap / valve to keep the exhaust going straight out the back of the car?

 

[superkarl]

Question?
Is the waste-gate to downpipe pipe ever going to get exhaust being blown up to the waste gate through back pressure? or is there some sort of flap / valve to keep the exhaust going straight out the back of the car?

The pressure and velocity is far greater at the downpipe end making it physically impossible for this to happen.

YouTube search some screamer pipes and be entertained

 

[badger5]

Question?
Is the waste-gate to downpipe pipe ever going to get exhaust being blown up to the waste gate through back pressure? or is there some sort of flap / valve to keep the exhaust going straight out the back of the car?

what back pressure would that be, vs the source of the "pressure" is the same point...

 

[Prawn]

As Bill and Karl have said above really Stuart. Such is the speed of the gas flow through the exhaust, and given how low back pressure is with an open 3" system, the exhaust gas just goes straight past the open hole really.

Any pressure that did travel up that way would simply find a closed wastegate. Or if the wastegate were open the pressure coming through from lae tturbo would be so much higher.

I'd like to write a big update today Bout how I got on really well last night, but I was so busy I forgot to take any pics!

 

[Rainbird]

Hand drawn illustrations will suffice. Animate it if you're feeling particularly fruity.

 

[Prawn]

Hand drawn illustrations will suffice. Animate it if you're feeling particularly fruity.

As you asked so nicely!

I did take one pic. Then forgot to take any more.

Jagged hole became round thanks to Handy power file from Dad:

 

[Stuart B]

As Bill and Karl have said above really Stuart. Such is the speed of the gas flow through the exhaust, and given how low back pressure is with an open 3" system, the exhaust gas just goes straight past the open hole really.

Any pressure that did travel up that way would simply find a closed wastegate. Or if the wastegate were open the pressure coming through from lae tturbo would be so much higher.

I'd like to write a big update today Bout how I got on really well last night, but I was so busy I forgot to take any pics!

Thanks for the details so that is a "screamer pipe" which I have seen in other posts and because there is no restriction in the exhaust boxes there's no back pressure and irrespective of any exhaust gas escaping up the pipe the gate is closed unless open and when open the valve would be at 20-30 psi and therefore overcome any exhaust pressure in any case.

Might any TIP injected water /meth catch on fire and spit flames through the exhaust pipe?

Why is the external waste gate diverted into the exhaust? safety?

 

[<tuffty/>]

Thanks for the details so that is a "screamer pipe" which I have seen in other posts and because there is no restriction in the exhaust boxes there's no back pressure and irrespective of any exhaust gas escaping up the pipe the gate is closed unless open and when open the valve would be at 20-30 psi and therefore overcome any exhaust pressure in any case.

Might any TIP injected water /meth catch on fire and spit flames through the exhaust pipe?

Why is the external waste gate diverted into the exhaust? safety?

Screamer pipes are obnoxious things... typically fitted because people lack the skill to fit them back into the downpipe and almost always pointing at something they shouldn't be... Bare in mind this is hot exhaust gasses so plenty of opportunity to set something alight...

What Prawn has isn't a screamer as its not venting direct to atmosphere... its simply a wastegate 'exhaust'... its vented back into the main exhaust as thats the thing designed to get exhaust gasses out the way...

If there was enough back pressure to force a wastegate open then you would probably lose boost anyway

For what its worth my wastegate opens at 8psi but creeps a little at higher revs due to the extended design of the wastegate outlet from the collector...

I suspect this may well be the case with Prawns as well but its not an issue as long as you are sensible with spring choice

Running a spring with less pressure and having a little boost creep actually helps drivability... big turbo hotsides are not flow restricted like K04 hybrids so tend not to need huge springs to keep a decent level of control at higher boost levels

<tuffty/>

 

[Prawn]

I think my current spring is 11psi, and I've got an assortment to try if required. It'll be interesting to see if it does creep much. As you say, it won't be an issue if it creeps a little.

Hoping to have the DP off and packed up this evening to post to Carl tomorrow morning

 

[Lavis89]

Hopefully I'll have it welded it up by the end of next week then look at getting back over to you

 

[Prawn]

I remembed to take pics!

So, now it's all tacked up, this is the wastegate connection in situ:

It looks tight at the top, but it's just the angle. There is actually a clear 20mm all round:

A view of how it runs from a different angle:

I marked all the joints on the car and their alignment, then before removing it I quickly made up the cat pipe I'll need occasionally:

I cut the end cones off the stock AUM cat I had so that they matched the 3" pipework, then tacked a length of stainless to each end and added v bands so it's easily swapped out. I'll weld this up myself, it's
mega heavy to post, and I don't want to send too much down to Carl as he' doing me a massive favour anyway!


I then removed the downpipe and wastegate sections and reassembled it all on the floor to check everything looked right:

Once marked up it was all disassembled ready to be shipped off to Carl:

Having never done anything like this I'm really happy with how it's come out!

 

[craigt1985]

Does everyone use someone from Babcock to weld up their exhausts?!

 

[Prawn]

Does everyone use someone from Babcock to weld up their exhausts?!

I have no idea what you're talking about