hopwood

Greg, that exhaust is a thing of beauty. Is it fitted yet? Do you have any video or sound recordings?

Cheers,

Joel

slate blue

Hi Joel, yes the exhaust was fitted back in 2006 and on a 4.7 litre with no tuning it did 277 rwhp on a dyno dynamics dyno and yourself being the UK would most likely have some experience with them.

I used to have a sound file, it didn't do it any justice, (on my phone) most people agree it sounds like a V12 and a bit like an F1 car of old, In fact the car that it sounds like is a Pagani Zonda at full tilt and you can here it from a long way away, however much like Ferraris but is quite at idle and has no boom. Those bypass valves are great except I have to remove it as the Government made it illegal here. That sucks because it would pass a sound test with the valve open or closed. We test stationary at 3,300 rpm, it is under full power that it is loud.

I can remember when I was going for a rego check and gave it a bit in this industrial area on Saturday morning, when I turned the corner the service station owner and a customer were outside and they said we wondered what the hell that was!

I said "We'll know you know"

Greg

Joel you probably haven't seen these other pics so here they are









And the redundant bypass valve, now unemployed

Iwanna928

Your work is meticulous and a thing of BEAUTY!

Stephen

UncleMaz

THanks Mark.

Ducman82

so if i get this right, a 4.5 rebuild with slightly hotter cams are good for Forced Induction, and a 4.7 with hotter cams and or stroked is better for NON forced induction?

checkmate1996

If I may...

My 5.0 hybrid (euro top end) COMBINED with the euro(ROW) g28-05 tranny makes it fast off the line.
What it cheap? Nope. It is fun now?? YEP!

The car is lighter with less electrical issues. With CIS, don't have to worry about your LH going out.
Another plus, is working on the engine is IMHO a lot easier. More room, etc. ( which equals cost avoidance versus working on 32v)
Also, I agree with earlier sentiments on knowing everything about your CAR, especially with these cars, versus buying unknown.
I also quit trying to figure out the money vs 32v upgrade comparison along time ago. This is my primary hobby where I spend my time and money on...
I will never sell this car unless I forced too from a fiancial needs position. Other than that, she's a keeper. I know evertyhing about her.
I am easily as fast as any stock s4 and then some...

mark kibort

Wow, those headers are real nice looking!!

Iwanna928

Anyone know the LSA for euro S2 310 hp cams?

Stephen

911tracker85

great thread, saving this link.

so far I am focused on refresh work on my US spec '84 928S auto, as I have only owned it for <2 yrs.

I have wanted a 928 for quite a while, and now it replaced my track/DE oriented 911 as a daily driver. a major part of the decision on an 84 was the low cost of entry, 4sp auto, and the simplicity compared to the S4. I have been doing my own wrenching so far. but one of these days I suspect I will want some more power.

for a constant level of HP increase, the suggestions in this thread cover that. what I see occasionally is postings for Nitros. for an occasional 'burst' of power on demand, that seems like a cheap way to go. of course the bottle refills and I understand the potental for nitros to be hard on the engine. from reading recent threads and a nitros vendor web site, matching with a progressive controller sounds like a good option. it will be at least another year before I get all the refesh work done I want to even consider more power. as a daily driver my interest is in an occasional burst of some added HP, consequently a 50-100hp shot of nitros looks like a potential solution.

not trying to stir this up too much, but curious about everyones thoughts on Nitros.

PS. look for the thread about Roger developing an improved intake. from the thread it not only looks great but adds a few HP. He has not gotten to the 16V version ... yet. drop him a note if interested to encourage his development efforts. knowing enough 16V folks are interested will help him justify the devleopment costs if he knows he will sell enough of them.

hopwood

Greg, I have a 1979 928 5 speed with an S2 engine and the original CIS injection and dizzy. Using an S intake and plenum. What would your recommendation be for an exhaust setup? At the moment I am using the original single pipe 79 system, and while it sounds great, I think it's throttling the car at the high end.

Options I am considering:

- 86.5 manifolds
- x-pipe into S2 dual pipe system
- y-pipe into custom single pipe

What do you think would be a good way to go?

Joel

hopwood

Oh, and another question about that exhaust - could you explain how the bypass valve works? Does it just open at high revs to make the car louder?

Fascinating stuff!

Joel

Steve Phipps

Greg,

Thanks for the info on the ball hones. I'll look on ebay.

How much time did it take to do the job? Most likely will take me twice as long, but nice to have an idea. ;-)

mark kibort

NOS is great. It has no ill effects on the 928 engine when done at moderate levels. I used a 75 shot for a couple of race seasons with no issues. NOS cools the intake charge and actually is better for the motor than the same amount of HP found the traditional way.

There is only one way to do it in my mind. Put the NOS button on the dead pedal to the left of the clutch. DONE! Have fun.

Mark

slate blue

Guys, I will try to get some more info and pics for you, as to time taken, I suppose I worked on those intake runners and plenum for a week or so, that included porting them and adapting the S runners to electronic injection. You have to go slowly with the die grinder as it is a dangerous bit of equipment. You can just see in the second engine pic how straight those S runners are. Then have a look at Dan Perez's runners in his avatar and 911Tracker85 see the bends, every bend is a loss. Not picking on you guys This is another manifold I made, it is straighter again, and is closer in equal length than the factory manifolds.




Joel, I think in the UK there is a seller of x pipes, blue flame if memory serves me, I think one of the big advantages the exhaust I have is low losses and high velocity. Impossible to achieve without a by pass valve. Have a look at the X pipe and imagine the relevant side closed off, it still works and flows in quite a laminar fashion. Other X pipes may not be the same so you need to examine that before choosing otherwise just make your own. I just put a metal blade in my wood table saw and cut it out like that.

The other thing I wanted was high velocity at the mix point, good pulse interchange, so that means the X pipe is 2.5" not 3" like the rest of the system. So as soon as it mixes, I expand it out to 3" and into one pipe on low engine loads, this keeps the column of air moving quickly and given that is the straighter side the losses are lower. I figured that after the X you also want the gas out, the work the pulses are going to do is basically done, so the lower pumping losses to get it out will lead to best engine performance. The bypass is is not about noise for me, it was about good drive-ability and power.

I will try later to post more info and answer PMs

Greg

slate blue

Here's a pic of what the bored out runners look like versus a standard runner.



This shows how the bottom of my runners are not closed in (squashed) like the S2 runners are.



This is the outside shot of the runners after conversion.



This is a look inside the plenum, another little trick, notice the runners line up, they wont unless you go through the process of aligning. Also the inside of the plenum has been slightly enhanced and has a tapered runner.



Greg