Turbo header size??

[Wentzel]

HI,

I want to re-do my turbo headers myself because I'm not happy with the result from a exhaust shop that did it the first time. What size pipe should I use for a 1776 engine that will rev to about 6500 using a b40 rajay turbo?? Round about 38mm or should I go smaller to about 32mm, don't want to restrict turbo but also don't want to hurt the response. Any advice would be appreciated.

Thanks in advance.

[Tony Z]

hey

I cant give you a 100% specific size but what I have piced up fromm reading the other forums is that you pretty much want to run a turbo header the same size as you would if it was normally aspirated.

eg, a 2276 with a engle 120 cam (street engine) would run a 1 5/8" header, then if you turbo it, keep that header size.
I would guess your engine to have a 1 1/2" header N/A, so go with that... 38mm OD.
If it is a mild turbo system and you are aiming for about 140hp, and/or low boost, less than 0.5bar, I would go with a 35 or 32mm header depending on whats available.

Please dont quote me, because I dont have first hand experience in turbos, only what I have read......

[IMPI]

I use investment cast 90 degree bends for my turbo headers and find them the easiest to use. The ones I used on the fastback measure 36mm ID and 43 od they weld easily and produce nice work. a Beetle exhaust port measures 32 mm and thus 32 id would work. Just remember turbos really like short headers. complicated 4 into 1 exhausts look the part but only produce slightly better numbers. most Factory turbo cars use very simple manifolds. I made 137 kw on a type four with a 50mm pipe linking the two heater boxes and the turbo flange welded to that.
Armand

[ZeroAxe]

Not trying to highjack this post, but think the question is inline with the topic...

assuming that you fabbed-up your own exhaust, in a Beetle/Bus, does a tuned exhaust really make such a BIG difference (read: equal header pipes)? The stock exhaust on a Beetle exhaust pipe is not 'tuned' (and not like in :"Hey! Howzit china!? ), hence my question. Does it really make such a HUGE difference or is it necessary?


Cheers!

[Surge]

assuming that you fabbed-up your own exhaust, in a Beetle/Bus, does a tuned exhaust really make such a BIG difference (read: equal header pipes)?

There was a very noticable difference when I changed from the stock pea-shooter setup to a tuned (freeflow) exhaust from TNT.
There seemed to be more low down torque (which I didn't expect) and the engine could finally rev nicely which makes a massive difference at 100km/h+.
With the original exhaust once I hit about 100km/h the back pressure limited the top end speed and the fuel consumption increased because I had to push the engine.
With the free flow (balanced) setup the bug cruises nicely at 120-130 without having to push it.

I don't think the balancing of the pipe lengths makes that much difference but the back pressure restrictions on the stock system are a real problem if you want an engine that can rev.

[Wentzel]

Hi,

Thanks guys I bought some machine bends a while back 1 1/2" about 38mm ID but now I'm not sure if it will be to big for a 1776 engine, its got 044 heads that has been ported a bit but I will have to check what size the ports are. Should I go to a smaller tube size?? or try 38 and see what happens, it's just so much work to waste if it doesn't work properly.

Any thoughts on this?

[Tony Z]

dont worry about what size the exhaust ports are. They are big enough. Inlets should have a fairly mild port job. Go with the 38 tubes. Unless its a race car (drags) I really dont think the pipes will be too small.
Turbo choice will be a lot more important a decision so make sure your homework is done in that department.

[Wentzel]

I' m going with the 38mm. Can't find information on my turbo Rajay b40b1, according to what I found the b1 is the smallest flow Rajay made and the 40 is the A/R ratio of 0.40. This sounds a bit strange and I don't know if this is correct. I am still working on the Turbo information but will hopefully get more info. The Turbo is on the car and made nice power before . . . and will again. The sizing can't be to far of if at all. Doing my homework at the moment and will fine-tune the setup after the intercooler and new exhaust is installed.

Still any advice or info welcome. I'm still learning.

Thanks

[Tony Z]

just keep reading. Do searches for anything you can think of thats turbo related. Read it all and slowly put the pieces together.

[Wentzel]

Thanks I will do that.

Can't wait to sort it all out though.

[eben]

Is that the turbo that came with the CB Performance "Cyclone Kit" ?

[Wentzel]

Hi eben,

I don't know but it is very possible, I bought it brand new separate a while back. Do you have any info on the turbo from that kit? or know where I can find any? Will do a search and see what comes up.

Thanks