Prawn and BigAls A3 Track Car

antwan64og said:

Whats the verdict on the new turbo/diff on track?

Does it perform as good as expected

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Jury's out at the moment Ant!

Curborough is such a tight and tiny circuit that the big 30 is never going to be well suited to it. Couple that with some borrowed road tyres that don't give anywhere near the grip I need, and suspension that I threw on last year and never actually setup, and it's hard to pick out the good and bad bits!

It was about 0.5s slower than I've done on a048s, and about 1s slower than my absolute PB set on Direzza 03G. But given the state of the tyres, and that its all new and untested I'm taking it as a fairly positive start.

The gt30 was always going to be worse at Curby, but Thruxton in 3 weeks time should be a very different matter!

Whilst I still plan to get round to writing things up, in the mean time here's a little in car clip from Monday:

Got some new wheels this week

scotty_24 said:

Your kidding? Not seen them every time Ive been on my phone in the last 24 hours ha ha ha

It looks amazing ! Cant wait for the arch mods to begin!

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I think you're following me around

Stuart B said:

Typical A3 / S3 drivers door impossible to shut. You need to push it shut with your bum prawn

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ALWAYS the case the cage padding is tight against the door card so it needs a good old Slam!

Life is complete!

Someone posted :O Didn’t expect that

Niels, thanks for the kind offer, it’s a lovely bit of kit, but I don’t plan on changing anything engine wise for a while now, it’s already plenty powerful as it is.

antwan64og said:

Nick, Do you you think big boy camshafts play a big part in some of the big gains for smaller turbos than yours?

https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1604750

Same manifold as you and made 500hp at Badger5 with WMI at 27psi on a plane Jane GT3071, its stil 1789cc and apart from being tuned for WMI the only discernible difference is the IE camshafts.

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Ant: cams play a BIG part in making decent power yes, but equally, how far you’re prepared to push it plays a huge part too.

The engine you linked to belongs to Gia, and happens to be an absolute freak motor, a bit like Bills Lupo. Sometimes, some engines just do more than you’d ever expect, and it’s often hard to pin point exactly why. 500bhp from 2 bar on a 3071 is indeed very good going, and the IE cams certainly seem to do the job!

On the NA cams we saw ~480 from around 26psi

We then changed a few things in the name of experimenting, and the car now runs a set of Badger5s more racey profile Cat Cams. We also changed the compressor wheel whilst we were at it, as the gen 1 GTX I had was pretty laggy compared to it’s modern counterparts, so we now have an AET 7+7 compressor wheel, which made very pleasing gains lower down when compared to the GTX J

The result is very similar power to before, this time making ~480bhp at just 24psi, and around 10lbft more torque despite the lower boost. It also spools a few hundred RPM sooner


We could well have pushed the car to 27-28psi, but it’s all too easy to lose track of what you’re trying to achieve with a project like this, and if I’m honest, I didn’t want all of it straight away, with nowhere to go if I wanted more in the future.

Looking at the difference between gate pressure at 10psi (300), and 24psi (480), it’s around 13bhp per psi of boost added whilst the compressor remains efficient (which it is at this level), so I’m sure if pushed to 28psi it’d be comfortably north of 500. Probably fine for a road car, but it’s power I couldn’t use, and potentially reliability I don’t want to give away.


As it sits currently, it runs around 24-25psi on the road, and feels utterly ballistic.


So much so that I’m still adapting to driving it really. My brain still wants to change soon after 7k, and the few times I’ve let it sing out beyond 7500 it just seems to get FASTER towards 8k. I think my ECU tell tale for max RPM seen is 8146 :lol:



I’m having the alignment done tomorrow, then it’s all set for Thruxton on Monday



I cannot wait to get it on a proper track and finally stretch it’s legs

antwan64og said:

I like how you say you’re keeping it at 480hp for reasonable traction on your FWD car

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Good isn't it

If provoked, it'll happily light up the wheels in 4th, but driven sensible through the gears it's absolutely remarkable how it puts the power down. 3rd and 4th gear are quite simply Devastating once you're on the move, 4th gear will almost double the national limit so I may as well send 5th and 6th back for a refund

It's mapped to be very driveable at the moment.
When I get the 265s on I may even find I have an abundance of grip, in which case its very nice to know i could quite easily dial in another lump of shove!

scotty_24 said:

I want to see this thing in the metal soo badly

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It'd be an absolute pleasure to dissapoint you Paul

It's definitely a 20ft car, but I love it

Stuart B said:

What happened to your rubber skirts?

Also is there a reason for the different colour wheels? E.g. are they wider or something, or just fashionable?

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What rubber skirts Stuart? I don't recall ever having any.

Wheels are odd colours because they've borrowed from a friend and these are all he had

A very rare quiet afternoon!

I'll attempt not to go into huge detail, but I'll try and do a mini catch up of what's been occurring lately.

Whilst the car was at Bills, we thought long and hard about it, and decided that we wanted to wrap up the engine mods once and for all. Do it once, do it right, and have something that hopefully we can leave as is for a few years to come and concentrate on developing other areas of the car.

The car had done very well as it was, but lag has always been in the back of my mind with the Gen 1 GTX turbo, and comparing my dyno plots to other similar cars it was clear that whilst the GTX flowed very well at the top, it was on the lazy side lower down when compared to the likes of the AET Bill normally fits to customer cars.

The decision was taken to send the turbo to AET to have one of their 7+7 Billet compressor wheels fitted as this is what Bill now opts for on his builds. We also had a new turbine and shaft for good measure, seeing as mine had been balanced several times and was a good few years old.

This came back looking absolutely beautiful!






So, whilst the turbo was off, it'd be a few days before Bill could continue on the car. The mapping was going to need addressing anyway on the revised turbo spec, so now seemed like as ideal a time as any to change anything else if we're going to.......

As fate would have it Bill had just removed a set of very low use Cat Cams from the Badgerwagen in the more racey spec. oooooooooooooh. I thought about these for a day or two, decided that I definitely didn't need them, then decided it would cost twice as much down the line to swap them over, change the cambelt, and take the car back to Gloucester to dyno it again, so just threw caution to the wind and went for it anyway

The cams were fitted and the turbo arrived back and went on that same afternoon:



Also whilst bits were off the car, the FID 1000 injectors from @StaceyS3 were tested.

I didn't actually get a video of this as I'd hoped, but the results seemed pretty good.

The injectors are based on a Bosch core, with a modified nozzle. These ones have a 15 degree pencil cone, much like the bosch 1000's I believe Tuffty uses:



FID claim that these will flow 900cc at 3 bar, with a variance of 1.5% between injectors.

We tested all 4, with the lowest producing 908cc, and the highest producing 916cc, so a max variation of 1.3% across the 4.

Spray pattern wise they looked very similar to the Bosch 1000s, which being the injector of choice can only be a good thing. part throttle drivability seems absolutely lovely with these, they seem to be smoother on transitions on / off throttle than I could get the car with the 630cc Dekas too, so I'm very happy with my injector choice

With the car all back together, it was time to get back on the dyno!

Bill and I chatted about what I actually wanted from the car, and the brief has always been to have it fast on track, whilst remaining as reliable as it can possibly be.

When racing you might do 3 20 minute sessions in a whole weekend, a warm up, quali, and a race.

On a typical trackday, I probably do 12-15 20 minute sessions in a single day! So 1 trackday isnt dissimilar to 4 race meetings in terms of wear and tear! When you look at it like that you realise that trackday requirements on the car are pretty extreme.

Having made 480 previously, we agreed that that was more than enough, seeing as more boost to make more power would result in more torque, which would more than likely just result in more wheelspin!

Bill set about tweaking the map to suit the new cams and turbo.

It was immediately obvious that the 7+7 wheel was doing it's thing nicely.

This isn't a finished plot, but this shows the difference in the spool up area of the GTX vs the AET. the 3 plots to the left are 7+7, the lazy plot to the right is the GTX for exactly the same duty cycles:



Bill did his tweaking, and the end result was an impressive 475bhp from just 24psi, with more peak torque made than the GTX managed at 26psi, and a decent improvement in spool too!



What can't be seen on the plots is the difference in response with the 7+7 wheel. I wish I'd known about the 7+7 wheel being available back when Dan rebuilt the turbo, as that's definitely the way I'd have gone from the start.

I have absolutely zero doubt that we could crank it up to 28psi and see well north of 500bhp. I believe the 475 was a repeatable figure too, run after run, not just a cold run to get a number from it, but a real world all day long figure, made at sensible boost, with sensible timing, so it should be as reliable as a 475bhp 1.8 gets!

So, with the car done, it was time to go and get it!

This meant facing up to one of my fears.....

A large metal box on wheels
It doesn't go from where you want to go
It doesn't go to the place you want to go

and it doesn't go when you want it to either.

Sounds great doesn't it?

Trains. Argh.

I got up bright and early, and left home at 0644 for the short walk to the station.

I got my ticket, and eagerly took my place on the platform waiting from the train to arrive.



Spirits were high, and the first leg to Basingstoke went fine.

As we neared Basingstoke, I checked the journey planner to see when my connection to reading was due.

Worryingly, it was showing an issue on the last leg of the journey, although it suggested that were was alternatives:



I asked at the desk, and was told not to worry, there were no delays, they weren't sure why the website was showing that. i had a brief walk around Basing to kill some time, then back to the station where my train to reading was on time.

Phew, onwards to Stonehouse!

I arrived in Reading at 0831 as planned, and set about looking for my 0903 to Stonehouse.

Hmmmmmmmmmmmmmm, this wasn't looking promising!



After much stress trying to find a human being in Reading station, I eventually established that ALL the trains from Reading to Cheltenham Spa (the line that passes stonehouse) had been cancelled due to a lack of drivers!



Argh.

I was eventually given a new route, which would take me via Swindon. Although annoyingly I had to wait almost 90 minutes at Reading, so I took a walk, had a maccies breakfast, and did a whistle stop tour of Reading Town centre. how lovely.

I got on the next train, and it wasn't long before I was in Swindon:



Another 45 minute wait here, so I went for a walk around Swindon too!

My final train towards Stonehouse arrived at Swindon at 1044.

It seemed quite ironic stood there on the platform; here I was, on my way to collect the fastest thing I've ever driven, and exactly 4 hours after I'd closed my front foot that morning, I was less than an hours drive from home still

Aren't trains amazing?

I finally arrived at my destination of choice! Some 5 hours after I'd left home!



A short walk from the station to Bills revealed some oddly cool places:



And I even arrived to a shiney black Audi A3 that had been washed by Mr B himself!



The drive back was good. Pretty boring for the first half just on the motorway. I can't do any high speeds in it because the wheel balance is awful and one of these borrowed wheels is slightly bent You really feel it as you approach 100mph. I can't wait to be rid of them!

Once thoroughly bored of driving my fast car slowly, I turned off at Hungerford and gave it some stick cross country towards home.

My GOD does it shift. It's reasonably peppy off boost, and starts to pick up before 4k, around 4500rpm it REALLY starts to move where it's boosting around 22psi, then somewhere around 6000rpm it lifts to 24psi and OH, MY, WORD. It really shifts then!

I know it's a often used cliche, but it's almost too fast for the road. not too fast as in dangerous or a handful, but simply because you can't put your foot down for any length of time, or through more than 2 gears at the very most, because it simply reaches insane speeds so quickly.

A cross country thrash now results in reaching your chosen speed insanely quickly then cruising because you don't want to be doubling the national limit every time you floor it

I absolutely cannot wait to get this out on a proper track. I think it's going to be epic!

Massive thanks to Bill for putting up with me over for years, and for having the car kept at B5 whilst I changed my mind about what I wanted to do with it! It's rare that I leave a car with anyone for any work at all, but I'm at a stage in life where sometimes my time is more important than the cost, and I knew it was in good hands, so it just made sense on this occasion.

After what feels like an eternity of building, and rebuilding the ****** engines in this thing, I think we're finally at a point where we can say it's done!

So, what's happened since then?

Mowgli and I had MacDonalds:



Then we went to Curborough:



The car was too low. lots of tyres rubbing on the wings:







It did look cool though

Nothing ground breaking speed wise there. the borrowed road tyres just wern't up to it and we were 1s off my previous PB.

It was however 357 miles covered in a single day with zero issues. A big tick for the car!



I got bored of waiting for Rimstock to make me some 10j wheels, so bit the bullet and ordered some 9.75 XXR 530's to get my by for a while:



These were fitted up with some of my BTCC 265 slicks



These were test fitted, and as you can see they fit great





A set of arch extensions were ordered. I went with the same set that @Golfyste uses in his golf, which looks absolutely epic:



Sadly, these just looked absolutely pants on the A3. Somehow the subtle differences were enough to just not work with the lines of the A3:



So a second set of arches were ordered!



These seem to suit the A3 shape much better, and cover my wheels very nicely without being too big.

obviously all these are just taped on in these pics, but it gives you an idea. the new arches sit so much better against the body, I don't think they'll be too bad to fit and get them sitting nicely at all

With Thruxton coming up I knew I needed to get the noise levels down on the car.

it had always been part of my plan to add a large centre section made specifically with quiet days in mind.

I measured up, and ordered the longest centre silencer I could possibly fit at 750mm:



This didn't take too long, I added a short section of pipe with a v band at either end, and made up a simple centre mount using box section to pick up my existing centre exhaust mounting:



I then nipped over to Andys to borrow his welder as the gas flow seemed to be decreasing on mine, and his is much better.

It's amazing what a decent welder with proper gas can do, even with an untrained idiot on the torch!



Not the worlds greatest welds, but more than good enough!

Centre section complete!



And fitted:



I can confirm the car now sounds like a silenced vacuum cleaner

antwan64og said:

Bwahahahahaha, lies all lies

It’s been a journey for you to get here, figuratively and literally. I’m glad to see you’re loving the results!

The 7+7 result is pretty epic considering you would expect the cams to push the power curve to higher rpm.

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Cheers Ant, the 7+7 was definitely worth while. These are the more racey Cams too at 268 in / 262 ex, yet we've still ended up with decent gains low down.