Throttle Bodies

[Preen59]

Just for the record, the ABF block in the white car is pretty much standard. It just has fresh parts, ARP bolts and a decompression plate.

TBH, I've built it to see how much boost it'll take before blowing up. It's actually RPMs that kill a 16v anyway; they seem to take a lot of boost for a long time if they're kept around a 7k rev limit

This is one of the other reasons it costs so much to build a nice ITB'd engine: the cams you need to actually use all that extra intake capacity demand so many revs, and you can't get much more than 7.5k out of a stock bottom end, and a bit over 8k revs from hydraulic lifters.

You also need to rev high enough to actually get a decent power band. If you didn't rev, you'd want a 7spd 'box!

There are huge improvements to made outside of the engine anyway. Putting a 3.94:1 final drive in a 16v 020 (and most 02As) feels like you've got another 30hp and your flywheel has shed half its weight. You can't really do this in a big boost engine as the torque will light up all the gears - you have to keep the longer ratios so it comes on a bit more lazily (unless have AWD of course). Being able to build a gearbox with taller 1st and 2nd, and then tighter stacked 3, 4, 5, 6 would be the best of both worlds, but that would be $15,000.

As Preen says earlier, getting near 200hp is great fun a Mk1 anyway I've only turbo'd mine out of curiousity - if the truth be known, it'll be a slower car in a lot of areas due to the lower compression, gearing, and the lag!

I agree with all that. The early oettinger engines were a 1.6 though. Well i'm pretty sure they were.

Techtonics Tuning told me that standard 16v internals (same rods as the 1.6, 1.7, 1.8 and early 2.0) will handle 25 PSI or around 8000rpm respectively. The thing to remember with VW engines is that the RPM is deceiving. They have a MUCH longer stroke than say a honda or toyota, and are actually over-stroked really.

Engines start running into problems with pistons generally around a piston velocity of 25m/s (metres a second), from what i've hear'd off most engine builders, above that the thermal load on the side of the piston becomes too great, with the addition of the increasing reciprocating force and BANG.

So at 8000rpm a VW 86mm stroke 1.8 has a piston velocity of 22.9m/s, very high for standard cast pistons. Although i was told by TT 8500 would be ok on standard internals.

A Honda 1.8 VTEC 77mm stroke at 8000 rpm has a piston velocity of only 20.5 m/s. Fairly mild, so you could rev it to say 9500 before you would run into problems.

[Preen59]

I suppose i should tell you how to work out piston velocity.. It's pretty simple.

Piston velocity is simply the speed that the piston is traveling at, at a given RPM.

We'll go with nice round numbers here to keep it simple.

Smokin Joe's 58 valve 4 cylinder has a stroke of 80.0mm and he sets his limiter at 9000 RPM.

RPM is revolutions per minute and we want a value in seconds, so:
9000/60=150.

Remember that in one complete revolution the piston goes from Top Dead Centre to Bottom Dead Centre, and then back to the top, so:
2x80.0=160.

Now, every one second at 9000rpm the engine rotates 150 times, so:
150x160=24000.

24000 is a figure in millimetres and we want metres, so:
24000/1000=24.

This gives us a piston velocity of 24m/s (metres per second) at 9000rpm.

I hope i've explained that clearly, let me know if i haven't.

[aprr32]

If you want honest 200+hp,reliable and driveable just put a 20v turbo in.No opening the engine to do mods,just wind up the wind and enjoy 280 hp at the fly with driveability that my even grandmother can enjoy.I've been down the highly tuned, bad mannered and short lived na's road years ago and while it's fun for a while, driveability is everything these days.

[GoLfMan]

I suppose i should tell you how to work out piston velocity.. It's pretty simple.

Piston velocity is simply the speed that the piston is traveling at, at a given RPM.

We'll go with nice round numbers here to keep it simple.

Smokin Joe's 58 valve 4 cylinder has a stroke of 80.0mm and he sets his limiter at 9000 RPM.

RPM is revolutions per minute and we want a value in seconds, so:
9000/60=150.

Remember that in one complete revolution the piston goes from Top Dead Centre to Bottom Dead Centre, and then back to the top, so:
2x80.0=160.

Now, every one second at 9000rpm the engine rotates 150 times, so:
150x160=24000.

24000 is a figure in millimetres and we want metres, so:
24000/1000=24.

This gives us a piston velocity of 24m/s (metres per second) at 9000rpm.

I hope i've explained that clearly, let me know if i haven't.

nice and easy! thanks mate im going to find that useful

[Preen59]

Righteo BDA fans, cop this! This is a post on a US forum from a tuner in greece. He's building a VW 2.1 16v to produce atleast 1000hp.

Here's the thread: http://www.vwfixx.com/forums/index.php?showtopic=25719

Ok lets talk about engines. Lets compare some of the best engines with the vw 16v engine.

First when i built an engine i determine the purpose of the engine and the rpm bandwith that i will need the power. How many horsepower i will need and the engine time limit.(reliability).

Reliability and power is something completly diferent.

2 things makes an engine broke : piston velocity and piston aceleration.
When an engine have long stroke the piston velocity goes higher. Typicaly 25m/sec its the limit of a normal engine. The abrasion of the piston inside the engine is very important. So a vw 2ltr engine with 92,8 stroke have 25,1m/s at 8100rpm. If we need to work this engine to higher rpms we must reduce the stroke, for example: from 92,8 to 85 (1817cm3) at 8100rpm we will have 23m/s so we can go to 9000rpm that we will have 25,5 m/s piston velocity. Some guys think that displasment is better than higher rpms. Thats stupid. I prefer an 1.670cc engine that revs 12000rpm thank a 3ltr engine that works 7500rpms. This balance is absolutely calculatable. All the mater is the actual flow of eatch engine lbs/min.Lets see an example:
3ltr engine with 8,5 comp.ratio and 7500rpm limit with volumetric efficiency 82% will gave us 62lbs/min. A 1,7ltr engine with 11 comp.ratio and 12000rpm limit with volumetric efficiency 82% will gave us 70lbs/min. The things are clear.
The other thing is the piston aceleration. Its very important the type lenght of rod / stroke ratio. The vw 2ltr engine have 159/92,8 = 1,713
1,6 - 1,7 is bad engine with rpm limit until 7000rpm max.
1,7 - 1,8 is good engine that can revs 9000rpm.
1,8 - 2,0 is very good engine that can revs 12000rpms.
So vw engine with 1,713 have 30000m/sec2 acceleration piston velocity and piston position from TDC 50000m/sec2 acceleration. When this prices reduces the best lenght to stroke ratio we have. My engine now have 2.105 length to stroke ratio and gives me the benefit to rev it until 12700rpm with no problem. For example a cosworth engine that have 90,8mm piston 76mm stroke and 130mm rod its better engine from stock 2ltr vw because have at 10000rpm 25m/sec 1,710stroke ratio. But thats only the design of the engine. Design of the engine cant give us power but can alow us to rev the engine higher. Cylinder head makes the power. Some theories tells that an cylinder head with bigger valves is better. Thats almost inacurate.
Typical its true but in real fact is mistake.Lets see the theory.
Vw 1.8ltr kr head have 117cfm inlet and 91,2cfm exsaust.
Cosworth have 122cfm inlet and 95,9cfm axsaust.
Theory tell us:
CFM x No. of Cylinders x 0.43 = BHP
Vw 117cfm x 4 x 0.43 = 201.24 bhp.
Cosworth 122cfm x 4 x 0.43 = 209.84 bhp.
Cosworth intake valve is 35mm and vw 32mm.
Typicaly the cosworth head its better BUT lets see it in action:
All the matter of power is how much mixture can pass at the same period of time.
Lets compare the 2 engines with same parts exaclty:
Vw 32mm intake valve 8000rpm limit and 10mm valve lift.
Cosworth 35mm intake valve 8000rpm limit and 10mm valve lift.
Cosworth 131,14 m/s flow mixture.
Vw 140.86 m/s flow mixture.
Thats the real benefit of the vw engine that noone knows.
The cosworth have 1005.16 mm3 valve open, vw have 942.33 mm3 but thats nothing to do with power / flow mixture per sec.
These years i am searching all the kind of engines i ve spent many many hours compare eatch other. Cosworth, Opel Vauxhall XE 16v, 3Sgte st205, Mitsubishi evo. Cosworth is the best of all the above and its more easy to tune.A good engine is more cheap to make it better but a normal engine is most expensive and dificult to make it better.I ve spent thousants of $ and private time to compare all the engines and to make the normal vw engine propably the best of all. I can write for hours but i have limited time.



Spyros

[Jarred]

yea, my head just exploded.

[twin eng, twin turbs]

Spyros is the man! reading all the posts he has in that thread is awesome. When i built the original atmo 1.9l 8v in Preens mk1 it had 42mm inlet 35mm exhaust valves, schrick 272 cam, porting and polishing, 10.5:1 compression, fully balanced, lightened flywheel, 1 5/8" 4 into 1 tuned lenght extractors 2 1/2" system and running on twin down draught 40mm webbers etc. The list goes on but my point is it was essentially totally worked for a nicely drivable street car but only made a maximum 170bhp. It is not easy to get big numbers from an atmo engine and keep it driveable or do it cheaply. I like webbers and ITB's but for out right power forced induction is the way, keep the revs down to below 8000rpm max and vw's respond very well to psi..

[Sharkie]

I used to run 2 engines on my Mk1. Both 1800 16v, the one with the turbo making close to 400bhp @fly (290kw) and a NA with 2x 45mm Weber SDs making 112kwatw (150bhp) or 130kwatf (175bhp). Enlarged (modified) throttle bodies in both cases.

You have to remember that this was at altitude (1800m above sea level) and included a loss of 18% (NA) and 11% (turbo) from sealevel figures.

The NA was a hoot to drive and used when the turbo motor was undergoing work...... we got swap over down to a couple of hours eventually as the turbo motor needed some work quite frequently.....

Watch the cam chain tensioner pully bolt as we snapped it twice (I still don't know how....) and had to redo the head once and replace it once.....

However notwithstanding a bit of lag down low, nothing touched it when it was on boost. Absolutely crazy and the most fun you can have with your pants on.....

[velly_16v_cab]

If you want honest 200+hp,reliable and driveable just put a 20v turbo in.No opening the engine to do mods,just wind up the wind and enjoy 280 hp at the fly with driveability that my even grandmother can enjoy.I've been down the highly tuned, bad mannered and short lived na's road years ago and while it's fun for a while, driveability is everything these days.

if your talking mk2 or 3 then a VR6 will give you 200bhp all day long

but yes, 20v T is the simple all rounder

[Valver.]

I agree with all that. The early oettinger engines were a 1.6 though. Well i'm pretty sure they were.

You're thinking of the 16s. Oettinger also provided aftermarket tuning packages for all 16vs Though, they were hugely expensive!