Cfm is the acronym for cubic feet per minute.

A measurement of volumetric flow, the higher the better.

Well said! We're essentially trying to move 70 x 1ftx1ftx1ft cubes of air into each cylinder every minute. That's a lot more air cubes than standard!

To put it in perspective: at full flow each of the 4 cylinders will be consuming the air from inside a balloon that's 5ft across, every minute. That's 4 big balloons acting as lungs.

Some Golf heads flow upwards of 100 CFM. But we don't need that much for the wee 1300cc motor.

Edited 3 February, 201214 yr by Tav

Which engine code is that then tav? 16v obviously...

Have you had a read of "Four stroke performance tuning" by A. Graham Bell?

Which engine code is that then tav? 16v obviously...

Have you had a read of "Four stroke performance tuning" by A. Graham Bell?

I'm dubious about books unless they come recommended? Is it a good read?

I was just looking up other cars on line. Honda B18 (ala Integra Type R) is 150CFM stock, or there abouts. Mind you it does have twice the power...

Its a very good read, recommended by everyone who reads it. Have a look on amazon...

Regarding CFM & cylinder heads, Taking a 1400cc engine as an example, how exactly does measuring its flow work?

Ah, cubic feet per minute, I see!

Makes alot more sense now. Thought it was about surface finish or something.

Cheeeersss

Come one, its nearly been 48 hours without any updates!

I've just finished fettling the ports on my cylinder head, but i'm afraid that i could be making it worse!

I've more or less blended in the casting marks, and "smoothed" off the short side radius to get rid of the sharp lip.

Have you got any more pictures? :-)

Shock & Awe

Rear coil over shock absorbers arrived from Gaz. I ordered them direct via email and was happy with the service. Answered all my questions and got a really good deal.

The springs are 165lb/in. as a starting place - standard Gaz spec. and the same as what Alex runs on his G40. Fronts are likely to be in the 200lb/in. range. This setup will be very road friendly. It's likely that the rear rates will almost double in future and certainly looking at fitting springs which will be firmer than the fronts.

They are adjustable on car with the control knob changing both compression and rebound at a fixed ratio.

I'm off to the garage to fit them just now...along with a million and one other bits and bobs to do!

Edited 13 February, 201214 yr by Tav

I love the updates it like reading chapters in a really good book

Edited 13 February, 201214 yr by residentmelon

Come one, its nearly been 48 hours without any updates!

I've just finished fettling the ports on my cylinder head, but i'm afraid that i could be making it worse!

I've more or less blended in the casting marks, and "smoothed" off the short side radius to get rid of the sharp lip.

Have you got any more pictures? :-)

Shaping up to be a great build dude! :p

What did you use to grind away and smooth out your ports dude?

Any recomendations? Is it recommended for the inlet manifold to be widened to? orr :)

Cheers

Hold the wheel and...

Watch a movie!? Recaro seat rails arrived today. Took them up to the garage with some blocks of wood to test fit the seat.

OMP WRC dished steering wheel also arrived today. So I popped that into the mix too. It's still not the best seating position but it's better than standard! Better than my Clio as well...though that's not difficult...

So comfy was the Recaro SPG I couldn't resist having some lemonade, a Wispa and watched a bit of a movie on my iPhone. Quiet garage, bliss.

The movie in question is TT: Closer to the Edge. Has to be one of the BEST documentaries out in the last year...maybe even better than Senna! Check out the trailer here:

Edited 14 February, 201214 yr by Tav

Looks great tav, When will be its first race? Would love to have a look!

Closer to the edge really is a very good movie. The footage is really really good.

I like Guy, but i don't like how he's a superstar now because this film revolved around him.

He's a real character though, which is why the film is mainly about him.

I hear folk say about 'that Guy Martin film'. It's pretty funny.

You talk about seating position: Is the seat lower? Higher? What about the wheel? Closer or further away?

Looks great tav, When will be its first race? Would love to have a look!

End if April...not sure I'll make it! But...don't have to do all the events in year 1. Will film it for sure! Open invite of course!

Seating position is improved by taking steering wheel towards you which lets you stretch out your legs a bit. Much needed!

I'd definetly be up for watching. Looking forward to more progress!

Don't suppose you need a venier pulley do you?

I'd definetly be up for watching. Looking forward to more progress!

Don't suppose you need a venier pulley do you?

I do actually...?

Bang on the Drum...71!

Cylinder Head Update #4

In a previous post I think I stated that Jason reckoned he could get the Polo cylinder head to flow 70CFM...well he was just about bang on the money! Latest results from the flow bench show 70.6CFM at .300" lift and 70.5CFM and .500" lift. To get this figure was a lot of hard detail work, making small gains with each modification. As always there is a graph to accompany the news! Look at the difference between the largest line and the smallest...looks good to me!

The dip nearer the highest lifts has returned, bugger! Jason thinks this is caused by turbulence. It's only knocking off 4CFM which as a percentage is quite small...but it'd be nice to get rid of it. More flow more power!

Still need to decide on a cam. Pretty much want the lariest we can get without modifying pistons. Think that restricts us to circa 280degrees and below.

Edited 25 February, 201214 yr by Tav

you know any more on the front shocks?

you know any more on the front shocks?

I've been meaning to get in touch. Everyone I contacted was useless/took a long time to get back in touch. Bilstein wouldn't/couldn't give the dimensions of their inserts except for overall length. Balance motorsport tell me Bilstein are too big/busy to deal with such small enquiries...which they agreed is frustrating and annoyed the hell out of me. Gaz got back in touch and said:

Mark,

Our inserts are for the large case struts only as we use a 22mm dia piston rod which is what you would need for this application, the insert casings are 44.5mm od & are 319mm long. They are not gas pressurised but do have a gas cell in them & these struts are used in the Saxmax Championship. You can run these with a lowered spring but not to low otherwise you will run out of damper travel & you will bottom out on the strut case.

If I remember rightly these dimensions don't quite match up with what you have?

You won't need 300lb springs on the back - there's literally no weight there. I've got mine turned to 2/3rds soft, it's about right.

Fronts at 275lb are quite firm, but not unbearably so. 225s would be more compliant but could introduce more roll into corners. Mine's really flat even through tight corners:

Compared to my old spring and shock kit - which seemed to ride worse.

(I ran both on the Speedlines, so not comparing 15s on the old kit to 14s on the Gaz stuff if you're wondering)

Mine doesn't seem to squat heavily under heavy acceleration either, forgot to add that before. And I've got the weight of a full interior in the back. You should be fine with the 165s and the shocks run slightly stiffer for track use. It'll be compliant enough for the drive home too.

Deutsch Freunde

Found a couple of interesting web sites this afternoon whilst buying bits. Nice to see a few Germans using the Polo for slalom racing, keeps the inspiration up! I particularly like the shots of the red and black cars below! I think I'll use this post to keep a list of other people I find using Polo's in anger. I hope to have a wee simple website after the car is finished.

http://www.rpt-motorsport.de/

http://www.slalom-polo.de

Edited 26 February, 201214 yr by Tav

Mine doesn't seem to squat heavily under heavy acceleration either, forgot to add that before. And I've got the weight of a full interior in the back. You should be fine with the 165s and the shocks run slightly stiffer for track use. It'll be compliant enough for the drive home too.

It's rare to get proper info on how spring rates work so thanks! The hills aren't what you'd call smooth, would be like driving up a single lane welsh hill road at 80mph. I think compliance will be welcome. If it understeers like a dog then I can just pop 200's on back and see how it works then go from there.

What kit were you running before? I had H&R's on my old car and they were fine for the road, just think coilovers will be better for this.

Mine doesn't seem to squat heavily under heavy acceleration either, forgot to add that before. And I've got the weight of a full interior in the back. You should be fine with the 165s and the shocks run slightly stiffer for track use. It'll be compliant enough for the drive home too.

It's rare to get proper info on how spring rates work so thanks! The hills aren't what you'd call smooth, would be like driving up a single lane welsh hill road at 80mph. I think compliance will be welcome. If it understeers like a dog then I can just pop 200's on back and see how it works then go from there.

What kit were you running before? I had H&R's on my old car and they were fine for the road, just think coilovers will be better for this.

I had a Spax kit before. It wasn't bad, but it's definitely more agile on the Gaz kit. I'd quite like to get mine corner weighted at some point but I'd say they'll tell me they can only get it so far. Weight distribution in Mk3s isn't great, but any improvement is good. That's how I see it anyway.

In the past I've just set it up using the car, adjusting a bit, use it a bit more, see how I get on, tweak again. It's not the most scientific method but it's done me fine.

I had a Spax kit before. It wasn't bad, but it's definitely more agile on the Gaz kit. I'd quite like to get mine corner weighted at some point but I'd say they'll tell me they can only get it so far. Weight distribution in Mk3s isn't great, but any improvement is good. That's how I see it anyway.

In the past I've just set it up using the car, adjusting a bit, use it a bit more, see how I get on, tweak again. It's not the most scientific method but it's done me fine.

I try not to think about the weight distribution 'issues' haha!

Looking Forward...

I was looking through some photos from last years season. Our camping facilities were somewhat rough and ready...I'm looking forward to more of the same this year!