930 Engine Rebuild & EFI question...

hobieboy · 10-16-2005, 06:31 PM

A bit of background - I'm starting my rebuild this winter after I dropped a valve chasing a GT-3 on the track last month

For those curious - I rebuilt the top end 2 years ago and promised myself that I'll never rev beyond 6200 rpm as my torque peaked @ 5000 at the time. Of course, new turbo, exhaust, cam & top end rebuild later, I build power all the way to redline. So, sitting in redline just a tad too long coupled with a redline heel&toe finally caused a valve retainer to dis-integrate and dropped a valve.

So, I've decided to be brave & aiming for a full rebuild + going EFI at the same time.

The question is: I plan to use a 3.2 intake which has a 41mm intake. I suspect with the turbo, I'd better off keeping the intake velocity higher during off boost hence should benefit from a slightly smaller intake size; say 38mm? Just wonder if anyone has experience or comments on this thought?

Second question: I am using a SC cam. What CAM would be better if I'm willing to tune the car for 90% track use (the other 10% is for driving to/from tracek)?

thanks...

strokher racing · 10-16-2005, 06:51 PM

I have owned a few 3.2 intakes. They usually range from 40-42mm. The port size depends on what kind of hp you plan to shoot for. Are your heads stock right now?

Eric Hood

strokher racing · 10-16-2005, 06:53 PM

As for the cams that will depend on how extreme you take this thing. That will be the last thing to address

Eric Hood

hobieboy · 10-16-2005, 07:45 PM

Eric, yes, my head is stock right now but planning on twin plug.
I'm tempted to port it to 38mm in a taper manner to match the 3.2 port size. Comments on that?
Cam-wise, would the Evo cam be a good choice?

strokher racing · 10-16-2005, 07:48 PM

Are you planning on doing the work yourself? How much hp are you looking to make? Yes EVO cams have proven to be great performers.

beepbeep · 11:04 PM

Did your say peak torque arrived at 5000 RPM on stock CIS engine? Weird. 930 has power peak @ 5500 RPM and peak torque was much lower than that. I never revved more than 6500, and that was just to bring the revs up when I shifted to another gear (beacuse of long gears). Power started falling off quickly above 6000 RPM on my stock 930 engine...it just made more noise.

Anyway, I suggest you port-match heads to Carrera intake and not to worry about port velocities too much. It's not as important as on N/A engines. It will mostly affect low RPM off-boost torque.

You will have some minor issues when it comes to mating Carrera flange to 930 heads though. 930 ports are smaller and injector notch on 930 head is placed slightly offset compared to Carrera notch.

Personally, I would ditch 930 heads and use Carrera heads alltogether. They already have correct port sizes and flanges.

hobieboy · 10-17-2005, 05:54 AM

Goran, well yes - my torque seemed to peak @ 5000 rpm before my last rebuild based upon my seat of the pants feel. With my current K27HF/cam/exhaust, torque/hp doesnt seem to dies off rapidly even at 6000; and on track, depending on gearing & track layout there are times that I "dont have a choice". When I broke the valve, that's the corner where I'm sitting in redline in 2nd from turn in all the way through track out (yes - a longer 2nd will help but...).

Wrt Carrera head - understand the issue but its a matter of $$$ isn't it?

Now I just hope that bending a valve will not cause any damage to the crank

strokher racing · 10-19-2005, 05:39 PM

Let me know if you need some headwork done and I will put you in touch with my head porter. He is as good as it gets. Your turbo heads can be adapted over no problem. Still need to know what kind of hp you are looking to make?

Eric Hood

hobieboy · 10-19-2005, 08:19 PM

Hi Eric, I don't have a real target hp to shoot for.
I decided to go EFI mainly because of throttle response improvements as well as reliability (fueling control). Based upon everything I read about my build, I am guessing 450hp would be a good guess?

strokher racing · 10-19-2005, 08:23 PM

If that is the power range you are looking to go into why not look at the EFI kits Stephen at Imagine Auto has. I am assuming you have dealt with him already since you are running a turbo from him. You could keep the stock CIS intake in the car and have a proven combo. The 3.2 intake would support more power, but doesnt seem like you are looking to make huge numbers.

Eric Hood

David · David's Garage

I buy from IA, so I'm not saying don't go there, but their kit is pretty expensive for a DIY and it uses the stock intake.

I'm nearing the end of a similar project and a few other Pelicans have finish their's. I've had some really long conversations with some of them and I still had questions I forgot to ask. Send a PM if you want to call and talk about it.

I'd open the ports to match the Carrera intake. I decided to go with 964 cams over Evo's. I had a reason at the time I just can't remember it.

hobieboy · 10-20-2005, 05:47 AM

Eric, its not that I dont want to make more power - its never enough, isn't it ?

But I just dont want to set a target of "I have to make at least 500hp" as I want to have a reliable engine that hopefully will last at least 100 hours (on track). Honestly, I have heard similar build to my existing CIS set up and folks are claiming 475hp. I'm guessing mine makes ~390hp - big difference that other than dyno difference I dont get.

David, do you mind letting me know more details about your build (& which EFI you went with?) and any significant gotcha that you can think of?

I'm sure I'll have lots of questions in the coming months

BTW - I'm going with Megasquirt, and probably start with fueling control only initially then add ignition once I get the base map running properly.

David · David's Garage

I haven't bought the ECU yet, but I'm still planning to use Autronic since Motec is a bit out of my budget (actually I threw the budget away about 8 months ago

).

I choose the Autronic SMC because is has 4 ignition outputs. I plan to send 3 signals to a M&W CDI to drive 6 M&W waste spark coils.

I've got the sensors ordered and I'll be building brackets and fuel rails over the next couple of weeks. You can use the stock Carrera TB, fuel rails, fuel damper, and fuel lines.

My only concern with Megasquirt is reliability. I'm not an electrical guy, I can build harnesses and wire them up, but I don't deal with what goes on inside the box. Maybe it's just my lack of understanding of this that worries me.

DonE · 10-20-2005, 05:13 PM

Quote:

Originally posted by 125shifter

My only concern with Megasquirt is reliability. I'm not an electrical guy, I can build harnesses and wire them up, but I don't deal with what goes on inside the box. Maybe it's just my lack of understanding of this that worries me.

If you are concerned about reliability, don't even consider the TEC3r. I've had mine back from Electromotive for 2 weeks and had the car at a dyno with an Electromotive tuner today, and we could not get the decel or idle to work properly - and that's with Electromotive tech support on the phone for 1/2 hour. On the way back from the dyno, the car died in traffic - I had to unplug and re-insert the wire harness plugs (no, really!) into the ECU. Started right up. To be fair, everything else seems to work.

hobieboy · 10-20-2005, 05:27 PM

Well, I considered 2 aspects of reliability: on the H/W side, there's stability of the circuit design and the assembly. I got my kit from Tbitz who seems to have good reputation from an assembly perspective. And he's local to me so hopefully support will be great. Design-wise: its a bit of gamble but judging from the hundreds (or thousands) that have used it, and its really a "simple" real-time control system

Then there is software stability... I have a software background so I thought in the worst case, I can read & learn the code and fix it. Then again, if many had it working...

For the price & feature difference, I can't tell myself to pay N times more for the incremental benefits from other systems.