Does it need a bigger exhaust?

[Chris bugster]

[ Attachment: You are not allowed to view attachments ]

This is a 2276 with an fk45, 44x37 home ported heads, 11:1, 48IDFs with 38mm vents and a 1 5/8 off the shelf header with muffler. Fan belt is on. Would a 1 3/4 help make more hp? This is a full weight  street car with a 3.88 r/p

[Chris bugster]

179hp is a good result, I believe, but wanted to get 5 or 6 hp more out of it because I offered a prize, a few years ago for the first na engine over here to exceed 180hp and it hasn't been collected yet. This is an engine built by a non professional engine builder with a bit of help from us and as its so close, wanted to change something easy to get it solidly over.

[Dougy Dee]

Bigger Vents!

[MeXX]

Hi...

38mm Venturies will defenitelly kill power @ 179 hp, a bigger exhaust might bring some hp too
I would change first to 40mm or even 42mm venturies (and they are more easy to change than the exhaust  )

MeXX

[Chris bugster]

Thanks, gentlemen. Will try some 40mm vents.

[neil68]

Ditto.  When I had my 44 x 37 heads, I started with 40 mm vents & 1 5/8" header.  This 2332 cc dynoed much better with 42 mm vents and 1.75" header. Stock weight Beetle got into the 12's in the 1/4-mile.

[Udo]

That exhaust is big enough. We have up to 240 hp with that on 2276 SS engine. 42 Venturies and may be IDA 's in the future

Udo

[Torben Alstrup]

X2 on the venturies. You might see that it pulls higher hp numbers but the driveability decreases. It is trial & error.
The torque seems a bit low, especially with 11-1 CR. It may be in the cylinderhead design though.
What header exactly?

T

[Chris bugster]

It's a VW Speedshop merged header with the muffler tucked away in the wheel well.

[Chris bugster]

Good point about the drivability. It is a full weight street car with a 3.88rp and .82 4th gear. It feels like a modern 16valve engine at the moment and I don't know how far we can go on larger vents before it feels like a full on race engine, meaning no power and then suddenly lots of power.

[Zach Gomulka]

Good point about the drivability. It is a full weight street car with a 3.88rp and .82 4th gear. It feels like a modern 16valve engine at the moment and I don't know how far we can go on larger vents before it feels like a full on race engine, meaning no power and then suddenly lots of power.

It's got a lot discplacement, stout CR, and a reasonable cam. You should be fine.

[Chris bugster]

Thanks for the kind advice. I haven't been here for a while and it's such a pleasant reminder how helpful you all are.

[DWL_Puavo]

Could few horsies be found from just a degree or two more total advance on ignition? The cheapest way until detonation 

Changing from 38 to 40mm venturies increase the venturi's area by 11% so it definetly should be noticeable if the venturies are the limiting the power. Main jet size should be also increased by about 10-15 when changing venturies but this is quite trivia. It should also be interesting to see if it effects in any way to the small dip on torque curve @4000 rpm - is it from some kind of transition in carbs or is it from the exhaust. May I also note that there's nothing wrong in those curves, but speculating is always fun!

What about your rockers, 1,4:1 or 1,5:1 ? Although they aren't any cheaper or easier to change than exhaust as you need to tune your rocker geometry etc.

[Chris bugster]

The ignition timing is optimised everywhere in the rev range as we made a little fully programmable computer and spent a lot of time on the rollers mapping it under various load- it takes a vacuum signal from the manifolds.
The heads are round port 39.5mm diameter. The combustion chamber was copied from the mighty mouse.
The rockers are Pauter 1.4 and springs are CB 650. Could have gone bigger on the rockers.

[Dougy Dee]

So those Dyno numbers were at the wheels? Stout little beast ...

[max Der Bahnstormerz]

I'd try the vents just to get him his prize, but the curves as they are are great for a street motor.

[Chris bugster]

Hi Max. Yes, we easily out dragged a 330hp Subaru up to about 95mph (end of 3rd gear) and so were very pleased as the original plan had been to only have something quicker than his other car, a new Golf 1.4 tfsi. It is such a nice engine as it is, especially the drivability but also  because the torque is relatively low and quite high in the rev range, so that traction is also very good and easy to modulate. A Quaife lsd is also planned for the near future. The first step will be a set of 40mm vents in the IDFs and then a set of IDAs which have been converted to throttle bodies. He likes the look of IDAs but wants it to be easy to drive and as the car already has a computer which can handle fueling as well, why not.