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Wastegate options on 91 turbo?

I've been searching and can't find an simple answer to my question so here goes.
91 Turbo, 44,000 miles, completely stock.

What are my options for wastegates, how much are they, where do I buy one, and is there a downside to upping the boost slightly besides working the engine a little harder?

Thanks
Brian

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Old 02-24-2009, 05:47 PM
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Quote:
Originally Posted by zbph10 View Post
I've been searching and can't find an simple answer to my question so here goes.
91 Turbo, 44,000 miles, completely stock.

What are my options for wastegates, how much are they, where do I buy one, and is there a downside to upping the boost slightly besides working the engine a little harder?

Thanks
Brian
Unless you're wastegate is misbehaving, you don't need a new or different one. If you want more boost, add a "dial-a-boost" or some such increase boost level control device. These devices work by adding pressure the the reference port on the WG. The higher the pressure on the port, the higher the boost level supplied to the intake before the gate starts to waste.
IMO, downside besides working engine a little (or a lot) harder by increasing boost is increase chance of detonation and serious engine damage or destruction. Unless you have an accurate handle and control of Air-Fuel-Ratio (AFR) and timing (more boost, less timing) your asking for trouble.
Going from 0.8 bar to 1.0 bar might buy you 15-20 HP. Is the risk worth the reward?
Sure, the factory boost level is conservative. That's why you've gotten to 44,000 miles and the engine is probably still running well. Add a little boost, lose a little engine life.
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Old 02-24-2009, 06:23 PM
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It is widely accepted that 1.0bar is the upper limit for safe-in-typical-environment operation if you have an adequate intercooler. The 965 intercooler is very good.
You can add a bigger spring to your stock waste gate, you can add a boost controller to your stock wastegate, or you can purchase a new waste gate from TiAL. Ben with M&K carries them.
As always, verify your AFR when making any changes in boost level.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 02-24-2009, 06:43 PM
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There are many many options.

The first three questions to answer are: how much money you have for this, how far you want to go and why?

At the end of the day, it'll be a combination of power/speed & money - directly proportional. Your call.
Old 02-25-2009, 11:23 AM
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If were only talking 15-20 HP then it's probably not worth the risk. The car is fast as heck anyway. With my 87 there was always something to work on (brakes, tune ups, interior, rebuild, etc) but now with this it doesn't need anything and I'm looking to tinker around a bit.

I put a cat bypass on and was thinking about an exhaust for a little better sound but I want the ability to go back to stock since it was totally unmolested when I bought it so my options on tinkering are somewhat limited.

Any exhaust recommendations out there, I'm amazed at how quiet the car is, I had a GHL and cat bypass on the 87 and loved the sound.

Thanks guys
Brian
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Old 02-25-2009, 04:02 PM
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General rule of thumb is 18HP/0.1bar

With Paul and Kirk's help I am working to mass produce this exhaust:

http://www.youtube.com/watch?v=wzhJt-hq714

.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 02-25-2009, 05:49 PM
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Then .7 bar to 1.0 bar is 54hp. That's quite a bit.

BTW the exhaust sounds great, if you need another "test car" let me know.

Thanks
Brian
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Old 02-25-2009, 06:24 PM
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If you want a "good sound" machine and a high quality product go with Brian's exhaust...

The best in the market!!
Old 02-26-2009, 03:31 AM
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I agree the 964 turbo can easily handle 1 bar so long as the car is properly tuned. The IC and WG are adequate to cool and flow the proper amount of air. So long as the diaphragm in the WG is Ok why spend the extra on a tial.

the 91 turbo came with .81 bar from the factory actual tolerance varies from car to car. The OBC will only show .7 bar no matter what spring you have.

I found the best muffler for sound weight and performance is the least likely you would expect. I have a 3" in out magnaflow that has almost 0 restriction and weighs 6 pounds saving a ton over that and muffler and sounds great. These mufflers only cost about $290 or so plus fabrication and aree as goods as any expensive muffler on the market.

I don't have a part number but you should be able to find it easily.

BTW figure without any changes except for the 1 bar spring an increase between 18 and 22Bhp. If you want to reduce lag do the cat bypass it is the best bang for the buck and I would also check you BOV they have a tendency to fail and might as well spend $100 to replace it with a billet version.
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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others

Last edited by Cobalt; 02-27-2009 at 05:08 AM..
Old 02-26-2009, 07:57 AM
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Porsche put a very good WG in there cars. As noted there is no reason to replace it unless it is broken. Tial dose not have anything on it.

If you are experiencing over-boost because of a larger turbo, that is a different story.

One of the best muffler set ups for a C2T is a bypass pipe to replace the combination cat/muffler section. The stock muffler can in the righ fender is very open. You can drop a tennis ball in that thing and it will come out the other side.

Going from .8 bar (1.8 atmospheres) to 1 bar (2 atmospheres) adds up to 11% more HP but that is only if your efficiency is not dropping off. (HP/1.8) x 2.0)) This, ((320/1.8)x2.0)= 355 hp with a one bar spring. This will likly triger your overgoost switch so you will have to deal with that.

I like the 3" Magniflow set up a lot to.
Old 02-26-2009, 07:34 PM
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Quote:
Originally Posted by 911st View Post
Porsche put a very good WG in there cars. As noted there is no reason to replace it unless it is broken. Tial dose not have anything on it.

If you are experiencing over-boost because of a larger turbo, that is a different story.

One of the best muffler set ups for a C2T is a bypass pipe to replace the combination cat/muffler section. The stock muffler can in the righ fender is very open. You can drop a tennis ball in that thing and it will come out the other side.

Going from .8 bar (1.8 atmospheres) to 1 bar (2 atmospheres) adds up to 11% more HP but that is only if your efficiency is not dropping off. (HP/1.8) x 2.0)) This, ((320/1.8)x2.0)= 355 hp with a one bar spring. This will likly triger your overgoost switch so you will have to deal with that.

I like the 3" Magniflow set up a lot to.
Normally and theoretically I would agree with you but more often than not the hp gain is not as much as you are calculation states for the 964 3.3 liter motor. At least from the cars I have seen this done to as a lone modification. Not sure why that is. The engines were known to be strong to begin with had no known vacuum leaks and should produce more but they did not. Basing it on the US spec which started at 315 hp the most power the charts showed for these cars was 335 & 340bhp give or take. However, using your calculation my turbo which started at 355bhp did come in at 333.6 rwhp or roughly 390bhp by just adding a 1 bar spring. So the calculation appears to work for my motor albeit a small % low. What is even more confusing is the 3.6 came with slightly more boost stock so the increase in boost is less than on the 3.3l.

On second thought I don't know who did the tuning on these other cars just what the results showed and that might have an impact if the car was not properly tuned.

Why do you feel a 1 bar spring will trigger the fuel pumps to cut out? This is normally set at 1.1 to 1.2 bar. If everything is working you should not have that much creep
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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others

Last edited by Cobalt; 02-27-2009 at 05:10 AM..
Old 02-27-2009, 05:07 AM
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Quote:
Originally Posted by zbph10 View Post
If were only talking 15-20 HP then it's probably not worth the risk. The car is fast as heck anyway. With my 87 there was always something to work on (brakes, tune ups, interior, rebuild, etc) but now with this it doesn't need anything and I'm looking to tinker around a bit.

I put a cat bypass on and was thinking about an exhaust for a little better sound but I want the ability to go back to stock since it was totally unmolested when I bought it so my options on tinkering are somewhat limited.

Any exhaust recommendations out there, I'm amazed at how quiet the car is, I had a GHL and cat bypass on the 87 and loved the sound.

Thanks guys
Brian
Go the exhaust route first before boost. The engine will not be as stressed because you are making it more efficient by reducing the backpressure on the turbo instead of cramming more pressure into the intake to get the power. Plus you can lighten the rear end of the car and make it louder at the same time with one of these high flow mufflers. You can always go bak to stock too.
----fred
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Old 02-27-2009, 05:34 AM
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Try one of these zork pipes.....though it is really loud.....I cannot say how much more power it makes by itself....have not driven it yet myself. Dam weather in Michigan.

http://www.youtube.com/watch?v=HmCQ_chad68
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Old 02-27-2009, 05:38 AM
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Quote:
Originally Posted by Cobalt View Post
Normally and theoretically I would agree with you but more often than not the hp gain is not as much as you are calculation states for the 964 3.3 liter motor. At least from the cars I have seen this done to as a lone modification. Not sure why that is. The engines were known to be strong to begin with had no known vacuum leaks and should produce more but they did not. Basing it on the US spec which started at 315 hp the most power the charts showed for these cars was 335 & 340bhp give or take. However, using your calculation my turbo which started at 355bhp did come in at 333.6 rwhp or roughly 390bhp by just adding a 1 bar spring. So the calculation appears to work for my motor albeit a small % low. What is even more confusing is the 3.6 came with slightly more boost stock so the increase in boost is less than on the 3.3l.

On second thought I don't know who did the tuning on these other cars just what the results showed and that might have an impact if the car was not properly tuned.

Why do you feel a 1 bar spring will trigger the fuel pumps to cut out? This is normally set at 1.1 to 1.2 bar. If everything is working you should not have that much creep
Sorry but my spell check did not work.

Porsche sized the K27-7200 almost perfictly to match the fueling of 930 CIS fuel head. What is happening with the C2T 3.3 is it dose start to run up against the limits of the turbo. Thus, it can not maintain full boost to red line.

The C2T 3.6 is alread at the limit for the 7200. Adding boost will mostly help in the mid range but there will be little gain up top.

The limit of the K27-7200 is in the 370-380hp range. Again this is about the limit of the fuel head. To deal with this Porsche changed the on boost control pressure that gets a little more fuel for the 3.6.

I would use that simple caluclation as the most just changing boost would get. In most cases losses in effecency will make the gain a percentage of this.

Changing the exaust increasses effecency with not change in boost. This can add HP. Changing the turbo to one with a larger more effecent compressor wheel will see increasses in effecency from not heating the air as much and allow the car to maintain boost higher into the upper RPM range.

The 3.6 if taken to 1 bar is potentally a 400hp motor. However severl things have to be addressed to do this. It needs a turbo cappable of supporting it, it needs a fueling strategy, it needs the restrictive cat to be removed, it may need the intake ports to be opened up a bit.

As to triggering the overboost switch. All WG's tend to overshoot there target at first and then stabilize at there target pressure. They also start to leak boost some before they hit there target level. Some of the electroic boost controlers go through a set up and learn how the WG responds. With this the can keep the WG clamped untill the desired boost level is reached. They also work on the other end to keep it from over shooting.

Not an expert, just my thoughts.
Old 02-27-2009, 06:15 AM
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Originally Posted by fredmeister View Post
Go the exhaust route first before boost. The engine will not be as stressed because you are making it more efficient by reducing the back-pressure on the turbo instead of cramming more pressure into the intake to get the power. Plus you can lighten the rear end of the car and make it louder at the same time with one of these high flow mufflers. You can always go bak to stock too.
----fred

Great idea! This increases the pressure differential on each side of the hot wheel for earlier boost onset, quicker boost build, and extended boost level up top.

Then if it is a 930, a better inter-cooler for another 20-30hp on the same boost.
Old 02-27-2009, 06:28 AM
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How would a better intercooler increase 20-30 HP on the same boost?
Old 02-27-2009, 06:38 AM
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Quote:
Originally Posted by 911st View Post
Sorry but my spell check did not work.

Porsche sized the K27-7200 almost perfictly to match the fueling of 930 CIS fuel head. What is happening with the C2T 3.3 is it dose start to run up against the limits of the turbo. Thus, it can not maintain full boost to red line.

The C2T 3.6 is alread at the limit for the 7200. Adding boost will mostly help in the mid range but there will be little gain up top.

The limit of the K27-7200 is in the 370-380hp range. Again this is about the limit of the fuel head. To deal with this Porsche changed the on boost control pressure that gets a little more fuel for the 3.6.

I would use that simple caluclation as the most just changing boost would get. In most cases losses in effecency will make the gain a percentage of this.

Changing the exaust increasses effecency with not change in boost. This can add HP. Changing the turbo to one with a larger more effecent compressor wheel will see increasses in effecency from not heating the air as much and allow the car to maintain boost higher into the upper RPM range.

The 3.6 if taken to 1 bar is potentally a 400hp motor. However severl things have to be addressed to do this. It needs a turbo cappable of supporting it, it needs a fueling strategy, it needs the restrictive cat to be removed, it may need the intake ports to be opened up a bit.

As to triggering the overboost switch. All WG's tend to overshoot there target at first and then stabilize at there target pressure. They also start to leak boost some before they hit there target level. Some of the electroic boost controlers go through a set up and learn how the WG responds. With this the can keep the WG clamped untill the desired boost level is reached. They also work on the other end to keep it from over shooting.

Not an expert, just my thoughts.
Makes more sense. I ended up changing out the exhaust and using a HF K27 to reach the 380 rwhp I am at right now. Boost comes up to 14psi and does creep ever so slightly to 14.8 psi but no where near the fuel pump cut outs

Quote:
Originally Posted by 911st View Post
Great idea! This increases the pressure differential on each side of the hot wheel for earlier boost onset, quicker boost build, and extended boost level up top.

Then if it is a 930, a better inter-cooler for another 20-30hp on the same boost.
I agree more is gained by changing out the exhaust than adding the additional boost.
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Gone worth mentioning '71 E '79 SC, '79 built to '74 3.0 RS tribute (2390 # 270 hp), '80 928 euro 5 speed, '74 2.0l 914, '89 944 S2,'04 Cayenne TT '14 boxster, '14 Cayenne GTS many others
Old 02-27-2009, 06:40 AM
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How would a better intercooler increase 20-30 HP on the same boost?
Dose not help on a C2T. That is one of the best IC's bar none. However, Andial did increase the core size on the 1992 S2 for Porsche.

On a 930 the intercooler is not very efficient. A more efficient IC cools the air better making for a more dense mix. This gets more air and fuel into the cylinder at the same boost level.

The only significant change between an 89 930 and a 91 C2T is the intercooler. This bumped HP from somthing like 285 to 315. Yes there were other small changes like fins on the cylinders, a mapped ignition, and a relocated oil cooler.

Old 02-27-2009, 07:09 AM
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Makes more sense. I ended up changing out the exhaust and using a HF K27 to reach the 380 rwhp I am at right now. Boost comes up to 14psi and does creep ever so slightly to 14.8 psi but no where near the fuel pump cut outs


I agree more is gained by changing out the exhaust than adding the additional boost.

I hope you have a fueling strategies as the stock system will not support that level of power.

Playing with some numbers just for fun: A stock 3.6T is 360hp, remove cat/muffler = 380hp. Add boost, 380/1.8 x 2= 422hp. Convert to rwhp, 422 x .85 for drive train loss = 360 rwhp.

Most dynos read differently than the Porsche factory numbers. For example my chipped, cat delete 3.2 pulls 217rwhp which would be 255fwhp.

My maxed C2T with larger IC core, big ports, big exaust, euro head, SC cams... and the K27-7200 pulled about 330 rwhp and would only get to about .92 bar boost. I did not dyno it with the K29 or HF/7006.

380rwhp is 447 fwhp. Very impressive.
Old 02-27-2009, 07:24 AM
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In an effort to reconcile my numbers above.

My 3.3 at .9 bar pulled 330rwhp. If I changed turbos and could pull 1 bar: 330/1.9 x 2= 347rwhp. If I make is a 3.6: (347/3.3)x3.6= 378rwhp. Adjust to for drive train loss 378/.85=445fwhp.

It is a match! Cool.

Sorry if I got carried away. Again, HP comes from increasing efficiencies (IC, ports, cams...) and from increasing boost.

Old 02-27-2009, 07:31 AM
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