75 1.8 Heat Exchangers options, Compatibility with earlier 1.8 or 2.0 heat exchangers Options

[jesiv]

I need to replace one of my heat exchangers on my 1975 1.8. Will earlier 1.8 or 2.0 heat exchangers fit? Thinking the earlier exhaust would improve performance. Are they compatible, improve performance and is it worth doing?

Thank you for the help!

Cheers

UPDATED

[wonkipop]

@jesiv

yep - you are right. same exhaust heat exchangers for 1.8 and 2.0 for 75 according to PET.

only difference was 49 state cars did not have EGR and CAT and thats all taken care of in the dual muffler section with a different bridging pipe and EGR pipe delete.

interesting. that can't have been ideal for the 2.0 L cars . possibly part of the reason for their slight horsepower loss in 75? (IMG:style_emoticons/default/idea.gif) the 1.8s theoretically did not have any horsepower loss.




which kind of goes back to your earlier question, would the earlier exhaust improve performance. theoretically it should not if the factory numbers were truthful.

the 1.8s stayed at 76 hp (or sometimes quoted as 73 depending on which way it was measured to which standard).

all the tweaking as we discovered in our research was to done with the double vac can distributor in 1974. they either hooked up vac advance for 49 state cars or didn't hook it up for california in 1974. thats pretty much all they did. then in 75, the 49 state cars had the vac advance disconnected as per 74 californian cars and the californian cars had the egr hooked up to the vac port on the throttle body (that in 74 had been hooked up to the distributor advance in 49 states) and the egr worked much the same as vac advance worked on 49 state cars in 74. really what it amounted to was that the exhaust system was more complex and costly in 75 than previously. but according to the numbers there was no performance loss for 75.

all they were trying to do with emissions was kill of NOX at idle and at cruise.
which they did first with retarding the ignition via the vac can.
and then in 75 move on to killing off CO with the CAT. the expensive move.
but VW and bosch managed to do it without big performance losses using fuel injection.
smart stuff.

they were some other factors. such as engines running hotter at idle in 74 and 75, and less fuel economy at cruise without vac advance hooked up on distributor.

so you could probably go with your original style heat exchangers (if you could find a set). and do it with a simpler muffler after that? if there is such a thing as a simpler muffler for a 75.

or flick it all over lock stock and barrel to earlier set up of 74.
but i doubt there will be any significant performance change.
it would just be about availability of the bits and pieces.

i think auto atlanta now have reproduced the later muffler so that at least is one stock 75/76 bit you can get again.

[Dave_Darling]

interesting. that can't have been ideal for the 2.0 L cars . possibly part of the reason for their slight horsepower loss in 75?

If you look at the design of the 75-76 exhaust, it's really far from ideal. Basically has a log manifold on each side, which goes immediately into a tight 180-degree bend. The driver's side crosses over to the passenger's side, which means that side is much longer. Very sub-optimal for exhaust flow.

I'm pretty sure that the exhaust is responsible for all of the power loss from 74 to 75. Backdate your exhaust and you should get that power back again.

--DD

[wonkipop]

interesting. that can't have been ideal for the 2.0 L cars . possibly part of the reason for their slight horsepower loss in 75?

If you look at the design of the 75-76 exhaust, it's really far from ideal. Basically has a log manifold on each side, which goes immediately into a tight 180-degree bend. The driver's side crosses over to the passenger's side, which means that side is much longer. Very sub-optimal for exhaust flow.

I'm pretty sure that the exhaust is responsible for all of the power loss from 74 to 75. Backdate your exhaust and you should get that power back again.

--DD

except there was no power loss in the 1.8s! (or so the factory claimed!)

and i think it was a 2 hp or was it a 4 hp loss in the 2.0s
which might have been down to other things as they had smog pumps on the 2.0s.
but not the 1.8s.

so.....i don't think the power loss was down to the exhaust?
sure its complicated. but you know an original VW style muffler like the 1.7s and 1.8s ran is not really a genius work of free flowing exhaust gas either?
the heat exchanger exhaust outlet looks very curvy etc but then it hits the dam wall of the muffler! so you know?
call me a contrarian. (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/biggrin.gif)

but i take your point. which is who knows really how it was affecting things across the rev band etc.

be interesting to have driven a 74 49 state 1.8 and then hop straight into a cali 75 back in the day when they were still pretty new and observe the difference if any.
not like either were fire breathing monsters. (IMG:style_emoticons/default/smile.gif) (IMG:style_emoticons/default/biggrin.gif)
and i say that in loving terms as i own a bone stock 74 1.8 and adore it.