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How much HP should a 930 w exhaust make?

Just wondering what the following 78-89 930 build might make or if anyone has something similar for reference.

Stock motor including stock turbo but with headers, straight through muffler, air pump delete, the AFR's & ignition set up on a dyno, and boost in the .8 to .85 bar range.

What do you think a build of this type might come in at?

Anyone changed the cam timing on a mostly stock but w exhaust turbo and seen any mid-range improvement?

Thanks for your opinion (s) in advance.
Old 01-11-2010, 01:03 PM
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I'd guess around 315HP at the flywheel.
Old 01-11-2010, 01:13 PM
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Much appreciated Jim, thx!
Old 01-11-2010, 02:08 PM
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Quote:
Originally Posted by 911st View Post
Just wondering what the following 78-89 930 build might make or if anyone has something similar for reference.

Stock motor including stock turbo but with headers, straight through muffler, air pump delete, the AFR's & ignition set up on a dyno, and boost in the .8 to .85 bar range.

What do you think a build of this type might come in at?

Anyone changed the cam timing on a mostly stock but w exhaust turbo and seen any mid-range improvement?

Thanks for your opinion (s) in advance.
The air pump is proven on a thread somewhere to enhance off boost response because it actually runs air through the turbo at lower speeds. That is all it does anyway, pump air into your exhaust. I might be tempted not to yank it without a lot of consideration.
Old 01-12-2010, 09:17 AM
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I think JFairman's is a good guess - but maybe even a touch (i.e. 10->15) more.

Look across "the pond" (Atlantic) and the European 1978-1988 cars developed in excess of 300FWHP (whereas, so I'm told, the U.S. 3.3 models only developed 265FWHP).
Old 01-13-2010, 04:09 AM
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Originally Posted by tj930 View Post
I think JFairman's is a good guess - but maybe even a touch (i.e. 10->15) more.

Look across "the pond" (Atlantic) and the European 1978-1988 cars developed in excess of 300FWHP (whereas, so I'm told, the U.S. 3.3 models only developed 265FWHP).
I believe my 1987 manual quotes 282 bone stock
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Old 01-13-2010, 04:53 AM
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Stock Euro is 300FWHP. Headers and muffler add 15HP, additional 0.1bar boost add another 15HP. Total ~330FWHP.
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Old 01-13-2010, 07:49 AM
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Originally Posted by mark houghton View Post
I believe my 1987 manual quotes 282 bone stock
Well, Mark, you may well be right. I'm just going from distant memory. (I don't have "The Porsche 911 Red Book" to hand right now.)

May be that Californian-type(?) states were more oppressive with their restrictions, and that's where the 265bhp figure relates(?)... It's just that the figure stuck in my mind because it's exactly the same as the 1977 3.0 RoW 930! (So bigger U.S. engine, intercooler, etc. only gets to where the Euro 3.0 to start with.)

Then we have to take into account the fact that Porsche Dynos every engine that comes off the production line, and the quoted figure is actually a minimum (when most manufacturers quote an average). I also know that in 1984, the peak torque was upped from 305 to 315FtLbs in Euro cars.

But anyhow.. Glad we're all agreed that the figure is probably somewhere between 315 and 330bhp at the Crank.
Old 01-13-2010, 08:11 AM
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Early stock 930 was US/Euro 245/265HP, '78-85 265/300HP, '86-89 282/300HP
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Old 01-13-2010, 10:24 AM
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Thank you guys.

All info is appreciated.

I suspect the stock intercooler and turbo would remain the most significant limitations.


My best guess might be 300fwhp starting point plus 30 for headers and straight through muffler, 5 for the air pump, 10 hp for boost bump from maybe .78 to.85 bar. 0-25 for dyno tuning of AFRs and ignition. Coming in at something like 345 to 365fwhp. Or something in the 290-315 rwhp range.

Maybe, maybe another 20 +/- HP dynoed to run on race fuel.

Thinking re-timing the cam might fill in the mid range to increase average HP a little and not over tax the IC and turbo to much. Might also reduce spool time a bit.

That is my thinking. I wanted to know what others thought or if someone had any dyno info for a build/tune that was close.

Again, thanks for the input.
Old 01-13-2010, 10:37 AM
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I'm not sure about this because I removed the air pump from my car right after i bought it when I did a valve adjustment. You have to remove the 2 vacuum operated diverter valves, a little air cleaner, and some hoses just to remove the upper valve covers anyway.

There are 2 vacuum solenoids mounted on a bracket side by side on an '86-'89 USA turbo and they are wired together in parallel from what I remember and I think they share their ground wires with the ignition coil ground wire.

One of these vacuum solenoids blocks vacuum from reaching the vacuum retard side of the vacuum pot on the distributor for the first couple minutes after a cold start so the ignition timing advances and idle speed raises about 300 rpms.
At the same time the other vacuum solenoid sends vacuum to the 2 air pump diverter valve so air is injected into the air injection nozzles in the exhaust ports to help burn whats left of the rich cold start mixture where it is still very hot.

When the K-jet ECU under the driver seat stops sending 12 volts to the 2 - 3 way vacuum solenoids after about 2 minutes the one on the right lets intake manifold vacuum go to the vacuum retard pot which retards ignition timing at idle to about 0 degrees or TDC which lowers the idle speed and increases exhaust temperature so the catalytic converter runs hotter and lowers emissions. At the same time the other vacuum solenoid also looses the 12 volts and it triggers the 2 air pump diverter valves to stop sending air to the exhaust ports and divert or send it into the catalytic converter instead where it will add oxygen to heat up the already hot catalytic converter so it burns up the hydrocarbons and unburned rich mixture while you are driving after the 2 minute warm up period... lowering emissions so they could sell these cars in the USA again.

I just do not see how that is going to give you 5 horsepower. I can only see this emissions system adding weight to the wrong end of the car and taking away a little horsepower while adding a little drag to the driver side camshaft to drive the air pump all the time and maybe adding alittle more wear to one side of the intermediate shaft bearing in the process.

My thoughts on the origonal question:
1. Stock 3.3 USA motor with cat, quiet muffler, and good flowing OEM later style exhaust sytem/heat exchangers is 282HP.
2. Take off the cat while leaving the stock muffler and you have about 300HP.
3. Put on a straight thru glass pack type muffler at least 2.75" ID, with 3"ID being better and you'll get about another 15HP.

So with nothing else changed from stock, my guess to the origonal question is about 315HP.
Old 01-13-2010, 12:00 PM
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Originally Posted by jfairman View Post
i just do not see how that is going to give you 5 horsepower. I can only see this emissions system adding weight to the wrong end of the car and taking away a little horsepower while adding a little drag to the driver side camshaft to drive the air pump all the time and maybe adding alittle more wear to one side of the intermediate shaft bearing in the process.
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Old 01-13-2010, 02:42 PM
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I borrowed the 5 hp number from a Porsche mag I have. Could be there tuner's guess.

Removing the pump would mean not having to spin the pump as there is no clutch on it. Still, unless it is under load there should not be much drain there.

I also saw something here that showed that the air pump did reduce lag to a deg. Do not know the total details on it except is seemed to be part of a Porsche engineering study.

Also, I read here that part of the procedure for setting the CO on a 930 with air injection was to remove the tube from the diverter or such but do not know for sure.

Thanks for the input.

Not a big deal.

I suspect most HP would come from a very low restriction exhaust and or more ideal AFR/ignition settings that pull some of the safety our of the settings getting the AFRs up from the 10's (most new car makers still run there turbos in the 10's for safety) and into the higher 11's or even low 12's and adding in more ignition advance.

Not a biggie.

Thanks again all.
Old 01-13-2010, 03:29 PM
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Originally Posted by 911st View Post
I suspect most HP would come from a very low restriction exhaust and or more ideal AFR/ignition settings that pull some of the safety our of the settings getting the AFRs up from the 10's (most new car makers still run there turbos in the 10's for safety) and into the higher 11's or even low 12's and adding in more ignition advance.
Yep, that's the ticket! And don't hessitate to ditch the 3LDZ and go with a better turbo, and a larger intercooler. All result in power gains. And once you've done that, crank your boost up to about 1.0 bar. That will bring you up around 360 fwhp with luck. But you already know that.....just couldn't resist laying it all out again. Really transforms the car.
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Old 01-13-2010, 04:57 PM
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not to completely derail this thread Iplan on dynoing my car tomorrow. Here is a breakdown of my car

stock engine - 76K miles
stock gearing
Carrera intake & throttlebody (with 3/4" tapered adapters to fit heads
double stacked stock intercoolers
K27-7200
B&B headers
straight pipe (no muffler, just 24" of 3" pipe)
Coil pack ignition
Megasquirt 2 fueling
93 octane

I plan on running 1 bar of boost but i'll post that info after the dyno runs
Old 01-13-2010, 08:00 PM
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Cool!

Let us know how it goes. (I'm guessing rather more than 282FWHP )
Old 01-14-2010, 05:43 AM
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Quote:
Originally Posted by 911st View Post
I borrowed the 5 hp number from a Porsche mag I have. Could be there tuner's guess.

I also saw something here that showed that the air pump did reduce lag to a deg. Do not know the total details on it except is seemed to be part of a Porsche engineering study.
5HP gain for removing a functioning air pump is reasonable especially if the pump system has the effect shown on this Porsche transient response data you refer to.


Old 01-14-2010, 06:31 AM
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That chart shows that you are better off with the pump as it spools the turbo faster.. so it's basically a small supercharger to aid in boost response
Old 01-14-2010, 09:11 AM
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Copbait73.

Thx for posting the study. I had seen that before but lost track of it.


Do we know if the air pump is only used as JFairman said? Only on start up to fire the cat.


If could be this test was done but the air pump is not engaged as it was during the study.

Also, they do not show any erosion in HP after full boost is reached. That dose not mean there was not any. Or, it could be they were thinking of using it for a boost and turning it off at full boost.

Wish there was more info to support the graph.

However, I is pretty cool.
Old 01-14-2010, 01:52 PM
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PS, looking at the graph, it looks like they may have been turning off the injection pump at 2500rpm.

Not sure.

Also, is not 3000rpm for full boost early for a stock turbo. Especially with a cat.

It looks like the pump almost takes 500rpm off the time to near full boost looking at P2.

Last edited by 911st; 01-14-2010 at 02:00 PM..
Old 01-14-2010, 01:53 PM
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