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rswannabe 04-17-2015 03:48 PM

Time to upgrade the 3.3 turbo in my longhood
In 2013 I bought an ’81 911 SC that was backdated to look like a ’73 RS. It also had a 1978 3.3 Turbo motor running through a short bell housing 930 transmission. I had been planning on getting straight into sorting some mechanical issues and upgrading the motor, but shortly after I got the turbo I found I needed to rebuild the top end of my other 911 motor (2.8 short stroke). I have a firm rule that only one car should be undriveable at a time. So while I rebuilt the 2.8, the work on the turbo had to wait. Of course that did not prevent me from accumulating parts and planning the work out. I have the 2.8 back together and running (fantastically) again, so the turbo is on deck.

The motor was rebuilt less than 10,000 miles ago with 8.5:1 compression, 964 cams, and a K27-7200 turbo. The rest of the specs are stock ’78 exhaust (thermal reactors replaced with short manifolds), a Monty dual out muffler, the stock intercooler trimmed to fit under a duck tail, and a pancake air filter. The car was running 1 bar boost when I got it, which I felt was WAY too much with the higher compression, especially on our marginal 91 or 92 octane fuel in Washington State. So I immediately located a 931 (924 turbo) wastegate spring and installed it. The 931 used the same wastegate as the 930, but with a spring only good for .5 bar. With this lower boost level I felt I was safe until I had time to fully sort the motor. I have not adjusted the WUR accordingly, so it is running pig rich under boost.

rswannabe 04-17-2015 03:51 PM

My goal is not particularly high power. Rather I want to achieve great drivability and response in an inconspicuous package for a long hood car. To me “inconspicuous” means no tail at all, and thus no intercooler. So my plan for the motor is as follows:

1. Ditch the 1978 exhaust for a set of GHL turbo headers I picked up from Spuggy.

2. Swap the Monty muffler for a Rarelyl8 Hooligan.

3. Replace the stock WUR for a Leask modified WUR I picked up from Spuggy.

4. Add a Safeguard knock detection system I picked up from Spuggy (beginning to see a pattern here?) and advance timing for good off boost response.

5. Remove intercooler and add a water/meth injection system tied to an electronic boost controller plumbed to the stock wastegate. When the water/meth tank is full and the system is armed, boost is higher (0.8-1.0 bar I expect). When the system is off or out of water/meth, the system reverts to just the wastegate with the 0.5 bar spring which I believe will be safe even without the intercooler.

6. Tune with AFR and Safeguard for safe, responsive fuel mixture and ignition timing.

7. Remove all the unnecessary and excess crap like the AC compressor bracket, air injection lines, front AC condenser, ext.

So, that is my plan. I’m interested to hear peoples input and opinions.

kenikh 04-17-2015 04:04 PM

And for the parts trolls... They have LONG ago been claimed and accounted for. ��

rswannabe 04-17-2015 04:12 PM

In preparation for this work taking place, I put the car on the dyno (Carb Connection in Kirkland, WA) to get a baseline before I start making changes. I am particularly interested to see the difference the GHL headers will make, as I think the stock exhaust is strangling the car in the upper RPM's. I was having some issues with the throttle linkage coming disconnected at high RPM's during the dyno pulls, so the plot below stops at 5,500 RPM, but it had already hit max torque and was only going to see a few more HP if any. It got 240 HP and 242 lb ft of torque. Assuming a 15% loss, that is about 280 at the flywheel at only 0.5 bar boost. Ignore the boost reading on the plot, as their sensor has been acting up. Per my 935 style gauge the car hits and hold a solid 0.5 bar.

As expected, the motor was running too rich under boost, more than 10:1. Boost comes on pretty well starting at 3,000 rpm, is at full boost and max torque by 3,500 RPM, and holds the torque peak to 5,000 rpm. Then it starts to taper gradually.

Considering a stock '78 turbo running 0.8 bar was supposed to make 260 flywheel HP, I'm happy with roughly 280 flywheel HP at 0.5 bar given the stock exhaust and current state of tune. I think there is a lot of room for improvement. I believe the GHL headers and Hooligan muffler will have the boost onset come earlier and be able to hold it further into the rev range. That combined with optimized fueling and ignition and I think it will be a very flexible and drivable motor. Then factor in the water/meth and 0.8-1.0 bar boost, and I think the total numbers should be more than enough to suite my needs.

patina 04-17-2015 05:10 PM

Talk about an awesome project!

Looks like you have pretty good plans - but why ditch the intercooler all together? Why not have one built or modified to fit somewhere in the engine compartment with some custom plumbing? You should have plenty of room on the passenger side considering you ditched the factory airbox.

rswannabe 04-17-2015 05:27 PM

Patina - My understanding is that if the intercooler is not in the tail/grill area, its not getting much/any airflow and thus is of limited use and just a heat sink. It also adds length and volume to the intake tract and hinders my goal of the most responsive motor possible. If I can meet my goals safely without an intercooler, that is what I'ld like to do. If I can't get the motor to perform well without an intercooler (not enough boost, pulling too much timing to avoid detonation), then I'll keep the duck tail and do a custom intercooler under it.

kenikh 04-17-2015 05:55 PM

Brooke, I have a water/air IC with a Bell core you can have. It should fit under a stock decklid. Supported 575HP on an FXT.

rswannabe 04-17-2015 06:19 PM

I'd like to keep the simplicity of no intercooler if possible. I'd definitely like to avoid adding the complexity of an all new water circuit, additional radiator.,pump and pipes. I know that sounds a little hypocritical when I'm talking of adding a water/meth system, but I see that system as a secondary level of performance that can be used or not.

mark houghton 04-17-2015 06:51 PM

Brooke, sounds to me like you've got your $$hit together and just kinda-sorta know what you're doing! One hell of a project with I'm sure fantastic results when you're done. Keep us in the loop! (oh...and if you can possible do an IC, then you should. The benefits are many).

kenikh 04-17-2015 07:24 PM

Just offering the option. You or Chris are welcome to it.

kenikh 04-17-2015 07:26 PM

And Mark, water-meth is technically speaking, a chemical intercooler. ��

rswannabe 04-17-2015 07:55 PM

This is the inspiration for what I'd like from my motor: a stock long block 930 3.0, 0.8 bar boost, non-intercooled, SC cams, K27, short headers, and a zork. The chart is from an engine dyno so the hp and torque numbers are at the crank. I'd be happy with this and I think it is relatively easily achieved.

RarlyL8 04-17-2015 08:31 PM

You're going to have to de-tune it to get those numbers. Seriously.

rswannabe 04-17-2015 08:35 PM


Originally Posted by RarlyL8 (Post 8582596)
You're going to have to de-tune it to get those numbers. Seriously.

Meaning I'm going to end up with more power? I'm ok with that. Or do you mean i'll need to drop my compression ratio and run more boost?

kenikh 04-17-2015 08:40 PM

Blow pure methanol and you'll have no problems. You're net octane number on pure methanol will be about 110.

smurfbus 04-18-2015 12:39 AM

I use a small container on the front luggage bay for both windscreen washer and WMI. Its pretty ghetto but for now its ok. I like your KISS method with only the meth for cooling and it should be just fine at those power levels. I have a small IC that fits under a straight lid but it does make maintenance a bit difficult so there is the key point for no_IC, IMO. Mine is a Turbo Kraft custom one, but IIRC they have a better bigger one available for ductail lids if you end up searching for some more power later on!

smurfbus 04-18-2015 12:49 AM

Couple more pics if you get interested in extra safety.

kenikh 04-18-2015 07:09 AM

That looks bloody fantastic. So fantastic, I want to remove my whale tail! And half regret selling my Ruf wheels. Gorgeous car.

RarlyL8 04-18-2015 10:53 AM


Meaning I'm going to end up with more power? I'm ok with that. Or do you mean i'll need to drop my compression ratio and run more boost?
Meaning you'll end up with more power. Just getting rid of that exhaust system is worth ~75HP if going to short tube headers. When we replace the stock 3.0L exhaust system with our tuned headers and muffler a 100HP increase results along with 1000RPM drop in turbo lag. The stock system is that bad.

kenikh 04-18-2015 11:02 AM

BTW, Brooke, is that a dyno sheet for Barrett's old car?

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