911SC (with CIS to EFI) Turbo Conversion

[1fastredsc]

Not only that but prolonged idle while sucking in air that is a little hot to say the least will cause the head temps to rise a little even if the megasquirt compensates for it. And as beep mentioned, if your not using an intercooler, that could be a major problem.

[beepbeep]

Well i wouldn't call it "a major problem" (eraly 930 didn't have intercooler either) as long as engine isn't pinging but it might make detecting a little hard.

Also, there are substantial HP gains to be had by using intercooler, you can boost more alternativly boost the same and get more power.

[tbitz]

I'm aware of the temperature rise due to compression. What I can do is place a temperature sensor at the intake of the turbo to see if the air temperature is above ambient. Here is a good turbo calculator that I use. It allows you to change many parameters and see the effect. You can try and see how much more power an intercooler can give you running at the same boost.

I cut my exhaust pipe and moved the turbo over to the right. This allows me to install the longer cone air filter. It also makes more room for the external wastegate. Also the turbo outlet lines up with an existing hole in the sheet metal. Does anyone else have this hole in the sheet metal? I'm guessing it was used for the smog pump.

[1fastredsc]

Thanks for the link tbitz. I'm trying to use the calculator so i figured i'd set all force induction things to zero and start from there. But when i use your numbers, go 0 atmosphere, and turn the boost and ic settings to zero i get 181hp and 176lbs of torque. Considering that sc's make about 195hp with just the back dated exhaust, not considering the efi kit, how do these numbers make any sense? And what is specific fuel consumpion?

[tbitz]

If you increase the "Engine volumetric efficiency" parameter you will get more Hp.

"Specific fuel consumption" is how much fuel is require to produce a given amount of Hp.

Read the notes at the bottom of the calculator for more info.

[1fastredsc]

I know what engine volumetric efficiency is, but the specific fuel consumption is what's throwing me off. How do you calculate that, or how would you find the information on that? Is it based on octane being run, or is it the efficiency of your internal combustion chamber design to absorb the energy released by the combustion process?

[emcon5]

Originally posted by 1fastredsc
I'm not positive, that's why i asked. I just figured a used 930 distributor would fix the problem. Maybe the existing sc distributor can be modified to retard under above atmospheric conditions?

I picked up a new old stock 3.0 turbo distributor off ebay for $300, so they are out there.

I don't know for sure about the 3.3 distributors, but the 3.0 distributor will not work on a SC engine as a direct swap, it spins the opposite direction You can swap the drive gear on the crank, but that involves splitting the case.

I noticed in this months Excellence 2 ads showing injector blocks,

http://www.turbokraft.com/ (whose web site is useless, at least from here)

http://www.patwilliamsracing.com/racedrivetrainefi.htm who sells a complete EFI solution.

Either may sell just the blocks.

Tom

[KobaltBlau]

Originally posted by tbitz
Can anyone who is running a turbo make a suggestion on a muffler. I don't want to be waking the neighbors in the morning. I'm also not interested in paying more for a muffler than I did for my turbo Maybe I should experiment with a dynomax?

Tony, I'm not sure if you solved this problem yet. I'm not running a turbo on a 911 but on another car lots of people are running magnaflows and they work pretty well. high flow, reasonable sound (probably louder than a 930 muff though) here are some:

http://www.magnaflow.com/02product/universal/oval.htm

they are pretty cheap and flow much better than flowmasters.

[tbitz]

Actually I picked up an oval magnaflow from the local auto parts store. I couldn't get it to fit properly. But I noticed they carry round mufflers too. I think the following will be perfect. I am going to order one, because they don't have it in stock.

6" round, 14" core, 20" end to end, 2.5" pipe diameter. link

If Mario Andretti says its good, it must be good

[1fastredsc]

It can't be any louder than a regular 911 with no cat and a magnaflow which sounds pretty good to me. My logic is that i was told the turbine blades in the turbo disprupt some of the sound waves making them inheriently quiter compared to a NA car with the same muffler. Can any of you comfirm this? Beep? You may just want to look at a way to quiet the wastegate dump tube, unless your dumping back into the muffler.

[ohecht]

Tony,

Are you planning to put the WB O2 sensor after the turbo?

I have read that it must be placed downstream to work due to the pressure buildup before the turbine, and I am wondering if you also see this as a requirement.

I already have the bung in one of my SSIs, and space between the turbines and were the exhaust tips need to be will be in short supply.

Olivier

[tbitz]

In order to read properly the O2 sensor has to be after the turbine and before any CAT. If you place it before the turbine the Increase in exhaust pressure will cause the sensor to read richer than actual.

I will be welding a bung on the intake to the muffler for my WB O2.

[beepbeep]

Turbo will kill high piched sounds, what comes out is deep roar that is best muffled using high-volume damper.

Small volume "straight trough" dampers aren't so helpfull.

[A Quiet Boom]

Originally posted by 1fastredsc
It can't be any louder than a regular 911 with no cat and a magnaflow which sounds pretty good to me. My logic is that i was told the turbine blades in the turbo disprupt some of the sound waves making them inheriently quiter compared to a NA car with the same muffler. Can any of you comfirm this? Beep? You may just want to look at a way to quiet the wastegate dump tube, unless your dumping back into the muffler.

Several years ago I stood next to Brian Sweitzer's Pro 5.0 8 second (at the time) Mustang, he was up against an open headered 5.0 on juice and you could barely hear the car. At that time his 5 or 6 inch exhaust pipe exited the turbo in front of the front wheels! about two feet of straight pipe from a turbo large enough for several Semi trucks I'd imagine. After he launched all I could hear over the roar of the other car was wicked turbo whine like a jet taking off!

[tbitz]

Originally posted by beepbeep
Turbo will kill high piched sounds, what comes out is deep roar that is best muffled using high-volume damper.

Small volume "straight trough" dampers aren't so helpfull.

Any suggestions on high-volume damper?

[cowtown]

Originally posted by tbitz
Any suggestions on high-volume damper?

Bump - I'd like to hear what beepbeep knows about this as well.

[KobaltBlau]

I think he just means a high volume muffler, like a 4x10" oval muffler or whatever they are. whether you have room to fit that is another story.

[beepbeep]

Huhhh uhhh (GWB style)...It's a difficult question as I don't know what kinds of mufflers are available overthere. Basically, you would want a single large muffler of "perforated pipe goes trough a barrel" type, as big as you can fit under rear skirt.

Pick a smaller one and you'll squash more of the medium-high range and less baritone but it won't kill the drone.

It all depends on your personal preferences and packaging issues. For max power, turbos like free flowing exhaust (with othere words, no "little backpressure is good for midrange torque" -nonsence).

It's a compromise and it's up to you to decide the level. Max possible size depends also on where you mount your turbocharger.

What are your preferences/priorities when it comes to sound, packaging and power?

[tbitz]

In my setup there isn't much room in there. A 6" diameter round is the max you can fit.

I returned my "cherry bombs" and ordered the 6" round magnaflow muffler. I'll try it out and see how it well it works.

[cowtown]

Originally posted by tbitz
In my setup there isn't much room in there. A 6" diameter round is the max you can fit.

I returned my "cherry bombs" and ordered the 6" round magnaflow muffler. I'll try it out and see how it well it works.

I'm running a Dynomax 3" in/out on my 930, and it's got a lot of low resonance. I don't think you could shoehorn a bigger muffler in there.

Case Length 16 in.
Overall Length 23 in.
Thickness 5 1/2 in.
Width 11 in.

Off idle it sounds good. It's loud, though.