Retro '75 build, just like you would have seen back in the day Options

[DanT]

nothing internal done to the muffler...just cap off the stock exhuast exit, and then drill two 2" ports for the new pipes. (IMG:style_emoticons/default/biggrin.gif)
all done intuitively, similar to a 911 sport muffler.
Just a little deeper sound than stock, and I like the look of the twin pipe!
(IMG:style_emoticons/default/shades.gif)
not loud at all as long as the internals stay stock.

[Tom_T]

I want to pass on a tip to Dan and all others with polished wheels or anything else in polished aluminum. There is a product called S100 corrosion protectant, that when applied will give you long term protection to the surface. When you buy it look for the spec sheet, you will be impressed. Not really a secret but we have been using it for years. I usually apply it before delivery to the customer so all that is needed is car wash soap and water to maintain that shine. Al Weidman

PS: Your worst enemy is brake dust that sits and gets wet.

Go here: http://www.s100.com/s100_cp.htm

[Tom_T]

nothing internal done to the muffler...just cap off the stock exhuast exit, and then drill two 2" ports for the new pipes. (IMG:style_emoticons/default/biggrin.gif)
all done intuitively, similar to a 911 sport muffler.
Just a little deeper sound than stock, and I like the look of the twin pipe!
(IMG:style_emoticons/default/shades.gif)
not loud at all as long as the internals stay stock.

If you have an old junk banana, you can cut it in half longitudinally & they can map it on computer CAD then map it for flow, & identify if there are any backpressure & vortices issues in any give outlet placement - all on computer, then tell you what to modify on the internal baffles.

Works even for mapping a stock 1 L outlet, & IIRC you can gain 10-20% performance improvement with the flow enhancing tricks, since it's the same idea as getting a tuned header exhaust system for racing, but on a limited scale using stock components.

A buddy had it done back in the 90's when he wanted to add a 2nd right outlet pipe mirroring the stock left, so they mapped it & he had to reverse/adjust some internal baffles to get equal flow L&R & avoid turbulence inside. IIRC he got about 20% more hp/tq just by better breathing.

Some guys think they can pull out the baffles for the same effect, but you still get vortexes in there from the shape of the"can" that won't allow it to flow so well. That's why the old glas paks that they used to sell for 914s were so skinny - to avoid the back pressure as much as possible.

[DanT]

If I keep this car the next HP increase will come from a 2056 running stock injection like my orange car was...or it will be a high revving small bore 6.
the 6 would be my preference, but who knows.

I am going to start some research on that type of motor in the near future...
A good friend of mine has years of experience building just that type of motor and will be a wealth of information. (IMG:style_emoticons/default/biggrin.gif)

this motor would have looked great in a my white car (IMG:style_emoticons/default/flag.gif)

[Tom_T]

(IMG:style_emoticons/default/idea.gif) ... is the 3-prong plug at the bottom of the pic for the electric motor, so you can run it as a rechargeable hybrid?? (IMG:style_emoticons/default/laugh.gif)

I like that motor, but not crazy about the orange tins & fan shroud - as I prefer the silver & black look personally.

I agree with the 2056 & D-jet idea, & I had considered doing that with mine (may still), but would probably pick up a core 2L motor for McMark to build a Raby 2056 & swap my matching nos. 2.0 case to save it as pure stock 2L for future CW purposes. I'd still love to drive it with the 2056's extra TQ & 110hp on the D-jet set-up though, even if I decide to CW it, since that could pass as a stealth upgrade at everything but Parade (if they were to check engine nos. there??). (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/w00t.gif)

For you & your AX use on this 75 2L - I'd think a 2nd engine by Raby 2270 - either carbed or "new EFI" with north of 165 hp & ???++ TQ would be the hot ticket - 200-300 lbs. lighter than the 6 with more TQ than the 6 at the low & mid-ranges, esp. vs. a high-revver!!?? (IMG:style_emoticons/default/shades.gif)

[koozy]

10-20% performance improvement with the flow enhancing tricks

Up to (or close to) 20hp increase on a stock motor with exhaust mods alone? I'd love to see how that is done.

[DanT]

10-20% performance improvement with the flow enhancing tricks

Up to (or close to) 20hp increase on a stock motor with exhaust mods alone? I'd love to see how that is done.

I was thinking the same thing (IMG:style_emoticons/default/biggrin.gif)

anyway, I am not a fan of type 4s that are any larger than 2056...just my opinion. If I want something bigger/stronger than that it will be a 6 or a suby swap. (IMG:style_emoticons/default/smile.gif)

[Tom_T]

10-20% performance improvement with the flow enhancing tricks

Up to (or close to) 20hp increase on a stock motor with exhaust mods alone? I'd love to see how that is done.

Geesh - give me a break! I did state "IIRC" & at the low end 10% is only 8.6 HP on a 75-76 2.0L (net SAE) ... (IMG:style_emoticons/default/dry.gif)

... but then you're assuming that a particular motor is actually putting out the spec HP, which is rarely the case, esp. to the rear wheels. .... & does he want to risk reducing the meager 86 hp of a GC 2.0 with a back-pressured or poorly flowing muffler (if it is - I don't know).

Check out some of the exhaust tuner ads - they typically claim 10-20% increases, but in the case of the D-jet it is also the restrictions on the other end - lack of air flow through the throttle body - so better breathing comes from both the "inhale" & "exhale" side. (IMG:style_emoticons/default/biggrin.gif)

Dan, there is no reason why the 2.0 can't be bored & stroked to more than 2056 & still run, and Porsche engineers back in the 70's looked at it as an answer to the power loss due to the post 75 smog controls, but didn't pursue it because the 914 was getting phased out by mid-1975 (early 76 MY).

In any case, better flowing less restrictive exhaust means better performance whatever the gain might be, and an owner customized exhaust may not perform as it was originally designed. Isn't that part of why everybody wants to back date their 75-76 2.0's to the 73-74 exhaust system!!?? (IMG:style_emoticons/default/confused24.gif)

So now, let's do the math - convert a 75 GC 2.0 to an earlier GA 2.0 exhaust system & muffler without the crap-alytic converter & go from 86 to 95 hp, well that sounds about like 9 hp or 10% to me!!!! (IMG:style_emoticons/default/biggrin.gif)
... yeah, I know - other stuff needs to be done to get the full step up to GA standards! ..... I'm just sayin'! (IMG:style_emoticons/default/dry.gif)

GoWesty builds some very reliable 2.3, 2.4 & 2.5L H4's - developed from our T-4's with higher output - so IMHO, more than 2056 T4's aren't a concern & we just differ!
(IMG:style_emoticons/default/shades.gif)

[DanT]

my GC motor has no air injection pump, and all ports have been blocked.
'73-'74 heat exchangers, '73-'74 muffler twin piped.
and the motor is fresh....so it should be pretty close to a 73 in power (IMG:style_emoticons/default/shades.gif)

won't be anything like my old 2056 (regardless of the color of the motor (IMG:style_emoticons/default/smile.gif)) but it will be a decent daily driver and AX PAX weapon. (IMG:style_emoticons/default/biggrin.gif)

[Tom_T]

my GC motor has no air injection pump, and all ports have been blocked.
'73-'74 heat exchangers, '73-'74 muffler twin piped.
and the motor is fresh....so it should be pretty close to a 73 in power (IMG:style_emoticons/default/shades.gif)

won't be anything like my old 2056 (regardless of the color of the motor (IMG:style_emoticons/default/smile.gif)) but it will be a decent daily driver and AX PAX weapon. (IMG:style_emoticons/default/biggrin.gif)

Hey - I always loved my 73 2L as a DD & went everywhere with it 130k mi worth, up to OR, UT, NV, AZ, NM, IN & PA once - a lot of it either going to play Rugby, skiing, vacations, etc. I cannot complain about a stock 914 2L - always loved mine! (IMG:style_emoticons/default/biggrin.gif)

... excuse my ignorance, but what is PAX or "AX PAX"? (IMG:style_emoticons/default/confused24.gif)

BTW - to each his/her own on colors, engine choices, CW or custom - so long as it's done well - & I can see from that pix that you do a great job on your cars! (IMG:style_emoticons/default/smilie_pokal.gif)

[koozy]

I didn't say it couldn't be done. I just wanted to know how so I could do it to mine.

[koozy]

Optimizing HP and torque over a RPM range suited for the type of driving one will be doing is not a factor of relieving back-pressure and increasing flow. (Ask me how I know) Velocity and optimization of scavenging is the key to HP and torque and where on the RPM range you will see the benefits of such mods. That would be the header first. Without knowing what to do with that, willie-nilly muffler mods will be of little effect.

[koozy]

Crap, I'm starting to sound like JP... (IMG:style_emoticons/default/laugh.gif)

[Tom_T]

Optimizing HP and torque over a RPM range suited for the type of driving one will be doing is not a factor of relieving back-pressure and increasing flow. (Ask me how I know) Velocity and optimization of scavenging is the key to HP and torque and where on the RPM range you will see the benefits of such mods. That would be the header first. Without knowing what to do with that, willie-nilly muffler mods will be of little effect.

With all due respect Mike/Koozy - Air & exhaust flow does indeed matter for engine performance.
Just try sticking a raw potato up the tailpipe & see what lack of flow does to it! (IMG:style_emoticons/default/lol-2.gif)
I recently had the catalytic ceramic inside the crap-alytic converter in our 88 Westy break loose, & every time it got up against the muffler inlet, the motor power dropped off like hitting a big headwind. (IMG:style_emoticons/default/blink.gif)

I don't know exactly what they did on the particular mods of my buddy's muffler, & it's a total package to tune an engine for sure. The tuners put my buddy's banana design on the CAD, ran their flow analysis program based on his stock 2L HEs (SSI's), & came up with the needed revisions to to make it flow L & R, which may have involved blocking the center to create essentially two shorter mufflers L&R.

Dan's taken a unit designed with internal baffles to flow R to L (looking to the front of the car) from the 2 L&R twin pipe inlets from the stock 73-74 2L HE's - sitting about 1/4 in from the L&R ends - over to the left single pipe exit - & he's changed it to exit in 2 pipes essentially about opposite the HE inlets. That may not be as bad a flow issue, as with my buddy's adding the twin pipe on the right end in a one-way flow muffler.

Dan also said he's got the air injection out - a good thing too, as it was a stupid system with little smog benefit which burned more valves than it burned the unburnt hydrocarbons!
... my first car, a 68 Opel Kadett 1100cc burned its valves due to that DA system! (IMG:style_emoticons/default/dry.gif)

Now Dan's also got the larger & better flowing 1-1/2" +/- diam. 73-74 2L HE's - which are essentially larger piped straight headers (as compared to the stock 75-76 ones) - although not as "tuned" as the racing headers, so his GC should be close to the GA's 91/95 HP.

You can also pick up about 5-10 hp just by using the Euro pistons & cylinders with the 8.0 compression ratio & high test gas at 100 hp (over the US spec 7.6:1 & unleaded 91 RON octane) - all staying at 2.0 (1971 cc) & without going up to 2056 cc (95 hp was old SAE std. while 91 was new SAE, but not sure which the Euro 100 hp was rated at, ergo 5-10 hp range gain). So obviously compression ratio & fuel quality also affect the engine' power & performance.

For everyday & variable driving on the roads, you want the HP & TQ bands as wide as possible, & the original T-4 GA 2.0 had a better low end performance due to the earlier & flatter/wider TQ band, than did the earlier H-6 2.0 of the 914-6 that it replaced. So the 4-2.0 actually outperformed the 6-2.0 below about 4000 RPM in stock configuration for both, which is where you want the pulling power around town, on the tight twisties & I would think in AX.

There are also lots of tricks that my old school mechanic knows to tweak the Type IV's to a bit better than spec HP & TQ. However, short of building a custom motor & fuel system like FAT Performance down here in Orange, Jake Raby (or McMark on 2056) & the other engine builders around do, it's hard to get too far out of the box from what the factory spec is! It all depends upon what you want your 914 to do & look like (OE vs. custom) & how deep is your pocket!

BTW Mike/Koozy - you almost made my point about flow mapping, but flow is a function of both velocity and volume. I can have a narrow stream with very little volume move very fast, or the same volume in a larger stream move slower with less "work" to move it, but the work can speed up the velocity to move much more volume than the smaller stream could ever move without a tremendous increase in workload.

Ergo, if I put in a venturi or decrease the diameter of the inlets or outlets anywhere, the velocity at that point increases, but that won't necessarily increase the power. However, opening the pipes up will also allow for increased velocity by allowing for a better flow, ergo flow mapping an exhaust system increases performance. Just like a larger siphon tube to drain your gas tank will drain it faster than a thinner or partially blocked tube - both given the same air pressure & gravity to drive the flow, because the flow is better.

And scavenging is more a result of piston top, head & valve design coupled with cam action primarily - so now you're talking about redesigning engines & that's beyond what I was talking here, & yet another mode of improving engine performance.
As Ron at FAT Performance says, he can design just about any engine you want based on what you want to do ....... for a price of course! (IMG:style_emoticons/default/biggrin.gif)

I don't know who JP is, but I guess now I sound like him too! (IMG:style_emoticons/default/confused24.gif)

(IMG:style_emoticons/default/popcorn[1].gif)

[Tom_T]

I didn't say it couldn't be done. I just wanted to know how so I could do it to mine.

I suggested getting a crapola 2.0 stock banana, cut it in half long-wise (keeping the internal baffles intact & in place, but cut in half), then take it to a custom exhaust tuner shop with the appropriate flow mapping software to mock it up & essentially redesign the internals to flow better - based on how many, what & where you want to put the outlets; then take a good muffler & pull it apart to do the mods.

However, most folks just go buy an Ansa, Bursch, Manta, Monza or Sebrign, etc. "performance" muffler, & assume that their factory flow mapping & design achieves what they claim it does to increase power.

[koozy]

Outside of engine component changes; dimensions of exhaust ports and piping are the varying factors of scavenging effects in the exhaust system (if we are not trying to bake potatoes. ie: block up the system with a radically restrictive muffler). I thought the discussion was about the exhaust and it's effects on "power" so I was speaking to that alone. I think you are mistakenly thinking I am discounting your assertion that mapping the exhaust is a good idea. To the contrary, I think knowing what to do with the exhaust is critical. I just happen to know that getting "more" flow isn't the answer. Having the correct "flow" is. If it were, we'd all be running 3 inch pipes.

[Tom_T]

Outside of engine component changes; dimensions of exhaust ports and piping are the varying factors of scavenging effects in the exhaust system (if we are not trying to bake potatoes. ie: block up the system with a radically restrictive muffler). I thought the discussion was about the exhaust and it's effects on "power" so I was speaking to that alone. I think you are mistakenly thinking I am discounting your assertion that mapping the exhaust is a good idea. To the contrary, I think knowing what to do with the exhaust is critical. I just happen to know that getting "more" flow isn't the answer. Having the correct "flow" is. If it were, we'd all be running 3 inch pipes.

(IMG:style_emoticons/default/agree.gif)

... I thought you were going a different direction before. I think we're probably saying the same thing, since mapping flow accounts for non-physical impediments to flow, such as eddies & vortexes, in the "plumbing" system on either side of the "big bang". In this case it was potential back pressure created by changing the flow pattern inside the banana muffler specifically.

BTW - we "baked a potato" in another buddy's muffler/tailpipe once back in the day - just to screw with him, & watch him keep coming back to the engine compartment to check everything over, as we pulled it out & replaced it each time. (IMG:style_emoticons/default/lol-2.gif)
Don't worry, it was payback for a series of pranks he'd pulled on the 3 of us on prior occasions, so just evening the score up a bit! (IMG:style_emoticons/default/biggrin.gif)

Apparently I'm not the only night owl on here! (IMG:style_emoticons/default/biggrin.gif)

[DanT]

geeze, do you two ever sleep? (IMG:style_emoticons/default/happy11.gif)

I am amazed you can carry on an intelligent conversation at such an hour (IMG:style_emoticons/default/biggrin.gif)

[Tom_T]

geeze, do you two ever sleep? (IMG:style_emoticons/default/happy11.gif)

I am amazed you can carry on an intelligent conversation at such an hour (IMG:style_emoticons/default/biggrin.gif)

The hard part is spilking, ..... err spearking, ...... uhh speaking intelligently at this hour after pulling an all-nighter working on stuff! (IMG:style_emoticons/default/biggrin.gif)

Actually I've always been a night owl & far better late at night, than for early mornings! (IMG:style_emoticons/default/wacko.gif)

Coffee! COFFEE! Where's my coffee!!?? ..... (IMG:style_emoticons/default/coffee.gif) ..... ahhh, the nectar of the Gods! (IMG:style_emoticons/default/blink.gif)

[DanT]

I am just the opposite....to bed by around 11:30 and up by 5:30-6AM....
(raised by farmers (IMG:style_emoticons/default/biggrin.gif) )

PAX= Performance Autocross index

a formula for comparing dissimilar cars at a particular event.