Exhaust modification comment

[2seater]

This is just an observation made while finishing my turbo install which may of some interest for those looking for a possible improvement using the '88-'90 exhaust manifolds. The outlet at the rear is actually off center to the left of the recess where the tailpipe connects to the exhaust. It "almost" looks as if it is made for dual exhaust. True dual exhaust sounds terrible on a V6, but it looks as if some definite improvement could be made to the stock system. Padgett suggested a sort of try-wye setup some time ago. The stock rear manifold could be cut to remove the #2 and #4 cylinders and remove the stock rear outlet. Install a true elbow at the stock exhaust outlet location aimed down in the stock location. This would be the exhaust from the front manifold plus #6 cylinder, just like stock. The outlets from #2 and #4 cylinders would have to be modified or better yet, hand fabricated into a small two cylinder manifold, 2" diameter would be adequate, so it can be routed down next to the original outlet. The two pipes can be joined at any point but the further down, the smoother it could be merged. The stock outlet which was removed earlier could be relocated closed to the Cat. or better yet, twin small Cats.could be installed, especially if they are staggered in the stock location and the pipes joined behind them. Maybe in the useless info category, but there were some questions some time ago. <img src="http://www.aaca.org/ubbthreads/images/graemlins/cool.gif" alt="" />

[Guest Greg Ross]

Hal,

I like information in the "useless info category"

Means someone has taken the time to ponder all this out and then to challenge anyone/ someone else.

Think I've perhaps mentioned (maybe several times) I went with the '91 (2 and a 1/2") system. And the Series I (a La '94)rear manifold is so dramatically improved for profile (what looks better usually is)

I ended up going "Legal" and used a high flo cat.

Just more for the "useless info category" <img src="http://www.aaca.org/ubbthreads/images/graemlins/blush.gif" alt="" />

And a BTW, and to answer your comment of a while back, the Series I was available in the Camaro with a manual tranny. That's where the Flywheel came from for my conversion, but thickness had to be cut down to suit the Getrag.

So the 3800 will take apparently take that crankshaft thrust.

Just a little more for the "useless info category"

[padgett]

I disagree with the remark about dual exhausts not sounding good on a 6, both the E-type (Inline 6) and Corvair (flat 6) sound great with true duals & even-fire 6 is no different.

OTOH unless you have a wild cam, a six does not need nor benefit from duals (so long as the pipe is big enough and collection is done properly) since the exhaust pulses do not overlap.

BTW the rental Maliblu (3100 v-6) I have at the moment has an interesting air cleaner assembly that has a much larger element than the Reattas yet looks as if it might fit. The air cleaner extends toward the engine *under* the intake hose.

[2seater]

Padgett, I agree with the comment about the Jag sounding good. The only Corvair I have had any experience with was a turbocharged one and the sound is "different", plus it was 30 years ago. I have recent experience with three different domestics and the sound is flat, to say the least. Maybe it has something to do with valve timing or compression ratio. Two have no cat. and one had twin cats. All sounded lousy to me, but of course that's all a matter of taste. GM, I had forgotten about the Camaros. That would be a car to do a modern GN type of installation. I agree the modern manifolds are better, plus the 2.5" is a bonus. Sometimes the benefit is just in the doing, not using what has been done before, kinda like your project. Perhaps useless is the wrong term, it's more like an answer to a question no one asked. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

[Barney Eaton]

I have some Corvair experience and it is interesting to hear a car coming that sounds like a Corvair only to realise it is a V6 with the cat and mufflers modified. For some reason, the 4.2 Chevy truck always fools me.

Are you guys saying that the newer 3800 header (firewall side) will fit the Reatta without modification? The crossover and downpipe fit without alteration?

[Guest Greg Ross]

[color:"#666666"] Are you guys saying that the newer 3800 header (firewall side) will fit the Reatta without modification? The crossover and downpipe fit without alteration?

Certainly the downpipe mates right up to either engine/ manifold, the swap to my new 3800 (externals from a '94 LaSabre) mated perfectly to the existing '88 exhaust. Then replaced that with the '91 stock (2-1/2") Reatta pipes. The check would be a simple matter-go to a NAPA or Auto Zone/ aftermarket for the PN for both '88 and '94 exhaust manifold gaskets. Same-same, same-same. Or not.

The '88 or '94 have to go as a set ie; you can't simply replace the '88 rear with the '94 rear only, the crossover connection is not located in the same place.

And Hal, exactly right,

The question no one asked,

I like your style.

[2seater]

Style? I'll take that as a compliment <img src="http://www.aaca.org/ubbthreads/images/graemlins/cool.gif" alt="" /> I did have my turbo project running tonight and I hope for a road test this weekend. Soon to be the only "remaining" turbo Reatta on the road.

[Guest Greg Ross]

Hal,

Congratulations, I tip my hat to you.

and

"Keep it between the Ditches"

Gee Haw

[2seater]

The turbo seems to work pretty well, although the car wants to run over cars ahead in traffic. It operates so differently since the turbo spools up quickly enough that there is more air available and it wants to keep accelerating without much throttle input. Nice strong push without any dramatic events as long as you stay out of the throttle at low speed. Tires spin at anything more than half throttle from a stop, but they are worn out and it's only 45 degrees here. Nice stable 7-8 psi of boost. Nice turbo whine at lower speed as it spools up but the exhaust has gotten quieter, even with no cat. My diagnostics refused to work today (climate control problem) so I don't really know what's going on inside the engine. It ran nice and cool though. If any of the turbo calculators are correct, should be in the 240-250 hp range. This must be similar to the low boost turbo Reatta the factory developed. They should have kept on developing it.

[Guest Greg Ross]

See you've updated your header pic to "an installed Turbo" makes for as quite a busy engine compartment! Your piping work to and from the Turbo looks like really neat fabrication.

I've achieved far less hp obviously but with the manual tranny direct drive I've noticed wheel spin happens on cold pavement if I put my foot in it, even up around 50 mph.

For that throttle attitude how about a robust return spring on the linkage!

And with this manner of installation, long term, do you end up with a burn mark on the Hood? <img src="http://www.aaca.org/ubbthreads/images/graemlins/tongue.gif" alt="" />

HoHoHo

[2seater]

No burn marks on the hood, or insulation for that matter <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> The whole system is ceramic coated inside and out (my single biggest expense), with no heat shields used except the small bolt on one below the throttle and cruise cables. The turbo does get very hot so radiant heat is an item to keep an eye on. Did you like the welded copper upper radiator hose? Much tuning needs to be done and this may change the heat radiation from the pipes which is acceptable right now. My previous stock manifolds are ceramic coated also, which I recommend highly. Gotta get that knock retard problem under control first. By the way, will the later model bag 'o snakes intake bolt up to my engine? I have magnified any air distribution problems in the stock intake by more than 50%.

[Guest Greg Ross]

I occasionally have knock counts go wacky but haven't connected it with anything specific. I'm a bit suspicious of several wiring connections made in the circuit for the VSS that are not soldered yet. Or not.

The other possibility, maybe the difference in impulses the sensor is hearing with the different Cam. Hasn't been a major problem, just one of several very minor things I'll be working on. What comes to mind is, is there a different knock sensor used on the Super charged engines?

Padgett, if you read this, might there be some option for some manner of filter to tame it down. I may be really reaching!

Do not know the answer to the Snakes Manifold question, PN for Gaskets "88 vs '94. If it is a go I'd suggest one of the early version aluminum cast vs the lattewr plastic for your temps.?

Did you get your Diagnostics going? I haven't studied responses to any great degree myself yet. I did specifically look at Timing advance while the Knock counts were spiralling with heavy acceleration/ lead foot manouvers and the degree advance really plunges/ auto retard with rpm? not knowing.

I must look seriously at the ceramic coating option, I know heat robs power so this a definite. Yes did notice the plumbing as well, pretty slick Hal.

[padgett]

Do not know about knock sensor and not home so cannot check part numbers. Keep in mind the actual count does not really matter, more of interest is *when* it dials in retard. With boost and a stock curve I would expect it to kick back particularly at heavy throttle opening/low rpm.

With a blow-through I would expect knock on any throttle opening since the air boost will lead the mixture change since will be pressurizing the pipe from the turbo to the throttle plate. Blow-through systems also run hotter. You might seriously consider water or alcohol injection to help cool the charge.

[2seater]

Yeah, I believe alky injection is on the horizon. The blow through was the easiest and cleanest installation, not necessarily the best. Still need to get a recording device to make sense out of what and when things actually happen. I have inquired as to the available programming information for the older GN chips and if the same is available for mine, maybe some sort of comparison could be done? High timing at first helps spoolup and response, and if knock can be controlled with alcohol, it should be a good combination.