SC Motor Long Term Development Plan

[longhornchris04]

So at my job I'm responsible for (amongst other things) long term planning. Applying this to my other interests, I decided to develop a long term plan for my 911's power train and I feel the need to consult the experts here on the board before I get to far. I've been surfing/searching these forums and here's the strategy I've compiled.

Unfortunately, I can't afford to implement this yet (government salary being what it is), but I hope this can drive my savings. Anyway, here we go.

The engine is a '79 3.0SC - mostly stock - transplanted into a '75 with Carrera flares. I'm running 205f/225r on 16s and can't get any bigger up front w/o body work or camber changes that I don't want to do. I mention this because I don't want to exceed my tires. OK, it would be nice to break it loose on command in 1st, but not burnout or anything.

The car is and will remain primarily a fair weather street car, but as I improve it I'd like to start autocrossing and/or do a track day every once and a while. My somewhat arbitrary goal is to have ~250HP at the crank, with the torque coming on somewhere around 4k so I don't have to rev the crap out of it on the street. Emissions aren't too much of a concern because Texas doesn't care about '75 and older cars. That said, I'd prefer EFI of carbs because I'm more comfortable with closed loop controls, etc.

So, first step is SSIs and backdated heat, for obvious reasons. No questions here.

Second step is to replace the CIS with EFI / ECU. I'd like to do full engine management (fuel + spark) because eventually I want to twin-plug. I'm currently researching both MegaSquirt and TEC3, but this choice will also depend on what is available when I can afford the upgrade. Part of the plan is to run wide-band O2 and mostly closed-loop. I plan on getting all the electronics to drive a crank-fire twin-plug, but only hook up single plug for now.

I do have a few questions. If not running a wild cam, is there any significant benefit to ITBs vs. the 3.2 intake? What about 3.2 intake vs. modifying the CIS intake (Bitz Racing kit), any substantial performance difference? Lastly, is sequential injection worth the extra effort compared to batch injection?

On the electronic ignition, is there a good way to install a knock-sensor on the SC motor? It would be nice to have the protection should the engine get hot. Alternatively, is it a good idea to retard the ignition timing if the engine is running hot to avoid knocking.

The general goal for the EFI / ECU conversion is to ensure that when I do a rebuild, I can do performance modifications without having to worry too much about CIS being a limiting factor.

The third step is to do the full rebuild. If my cylinders are reusable I'll stick to 3.0, if they aren't then I'll upgrade to a 3.2SS (if I'm buying P+Cs then the cost differential is nil). Heads will be polished and twin-plugged (hence getting the twin-plug ECU earlier). New pistons with an increased compression ratio (there will be a question), and a regrind on the camshaft to take advantage of EFI's better flexibility. Standard machine work will be done per Wayne's book, as will reliability mods. So, on to the questions.
- I'm going to run on pump gas, how high can I get on CR? Will this be different for the 3.2 vs. 3.0? Is 10.5 too high?
- Still on pistons, are piston coatings worth the investment? Specifically dry-film lubrication on the sides and/or ceramic/thermal coating on the upper surface.
- What are my options for camshafts, keeping in mind this will primarily be a street car and I want it to have decent torque down low? I was thinking about the 964 or S grind... but I'm not very familiar with my options in this area so I could really use the advice. Also, with these recommendations comes the valve spring issues. I'm planning to replace the springs (cheap insurance, while I'm in there) but would definitely upgrade if the camshaft needed it.
- For oil circulation, will the SC pump be enough, or should I upgrade to one of the later style pumps? This may be a non-issue as my current sump plate is the plug-less variety, so I may already have a Carrera or Turbo pump.
- For oil cooling, I have the 28 tube brass cooler. Is this enough, or should I plan to upgrade to the Carrera cooler? Worst case I do this post rebuild if the temps are higher than I like.

So, there are a lot of questions here. My plan is to save this thread and look back from time to time, adjust my budget start gathering parts as I can afford them. Hopefully they will help others who are in a similar situation

So, I bring present my questions to the Engine Forum. Thanks in advance for your help.

[jaybird840]

Maybe Jamie Novak will chime in here. He is running a megasquirted 3-something car, and seems to have a great bit of knowledge of the subject..... Jamie?

[JohnJL]

Good idea to plan ahead.

I have a spare megasquirt for sale with the EDIS control units and coils and wires. Cheap.

For a fully-supported, fully-featured and tough EFI system without the MOTEC cost you should have a look at Adaptronic (www.adaptronic.com.au) also.

[longhornchris04]

JohnJL - if only I had the money. Right now I'm getting ready to move. Uncle Sam has decided I'm off to Wright Patterson AFB (Dayton, OH). While they cover the moving costs, much of it is through reimbursement. No cash means no upgrades. Plus I don't have a good shipping address for the next couple of months.

Of course if you haven't sold it in a few months I may be in touch.

[euro911sc]

Your steps sound good. Problem is that the CIS pistons are going to get in your way. Those are going to have to go and probably when you do the EFI. Though I guess you could EFI and stick with the CIS parts... need to get an answer on that question. But, if you are changing pistons you might as well get bigger stuff. Also, if you are twin plugging the heads you might as well take the whole engine apart. In my limited experience, the top end is the hard expensive part. Bottom end and case is easy.

The really nice thing about ITBs is they look and sound REALLY cool and the install is a lot cleaner. A hacked up 3.2/3.0 intake looks exactly like that... a hack job. Don't get me wrong here... they work great! and are a cost conscience solution that you should consider.

I'm not sure, but you may want to combine steps 2 & 3. Cost may prevent it, but you may save inthe long run.

Best reagrds,

Michael

From Jeff Alton's Car:

[sjf911]

Be careful to stick to your plan or you end up with this.



I had the same desire spurred by the need for a top end rebuild. I went EFI with megasquirt also controlling EDIS based twin-plug electronic ignition based on a Carrera 3.2 intake and fuel rails. I opted to upgrade the P/C's to a 3.2ss at that time, although this adds significantly to the expense. Using SSI's and an OEM muffler I was able to hit almost 230 RWHP. This was with 964 cams which do delay peak torque above 4500 RPM. ITB's would be a great option and I debated this but ultimately I had the notion to try to turbocharge my car so this swayed me to the 3.2 intake. Things have continued to slide down the slippery slope since then.

[longhornchris04]

Michael, Steve - I know the CIS internals, will hurt performance in the short run after the EFI conversion... the question is how much because unless I win the lotto (tough when you don't play) I can't afford the EFI conversion and rebuild at the same time. Unless I'm willing to wait even longer. I was hoping to have at least 2 incremental performance improvements before getting the final motor.

That said, it is my plan to address "everything" while I've got the motor apart. The EFI conversion won't include modifying the long block at all, save installing sensors.

[jpnovak]

Since you want to do this in steps let me shed some light. I did a similar thing.

My route was a 78 3.0 SC motor. First step was to ditch the CIS when I put it in the early car. The car was quick but lacked top end. To me the motor was very flat above 5500. Not what you want in a lightweight early car begging to run to redline at the track. The car drove like this for several years.

The second step was to convert to ITB/EFI. While no internal changes were made in the motor this made a HUGE difference in the feel of the car. Throttle response was crisp and there was a noticable increase in top end power. I think that part of the problem was that the weber 40s were choking off the motor at high rpms.

The cams choice and plenum/intake choice are closely related. An agressive cam will have a strong reversion signal that will confuse the best injection systems (think CIS air meter/motronic barn door/EFI MAP sensor). There are ways to get around this problem using cams. the easiest is to establish a relationship with a good cam grinder. HMM What do you know there is a great one that frequents this board and his name is John Dougerty, aka: camgrinder. So he might suggest a cam that would clear CIS pistons, have high lift (exhast side limited) and decent duration while at the sametime having a wider lobe center. This will give better performance with your injection system, give you a wider torque curve and still give you the mid to top-end performance you are looking for.

A common plenum system will help balance the reversion signals from the cams. when using ITBs you must have a balance chamber that pulls a vacuum signal to a single plenum, neutralizes the signal pulse variations and sends an "average" value to the MAP sensor. otherwise the reversion pulse from your new cams (even stock SC cams are bad for this) to the ECU. The reversion pulse will read like a millisecond time scale change in MAP reading and make tuning a complete nightmare. Been there, done that, kicked its a$$.

I am willing to bet that with a few hundred $$ in a cam upgrade, a 3.2 intake and a MS EFI system you will outrun many of the cars around. This would be a very fun car. In fact, if you plan accordingly all these parts could be considered to keep you in a stock class (MS excluded) but you could install motronic and chip the car.

Overall the Megasquirt system is extremely capable. I have not yet found a feature that I want that I can not do. This may mean editing the .ini file with custom code and installing a few jumper wires but that is what I like to do. MS is a DIY system and you MUST LEARN EFI. You will not get a turn key setup with MS. Failure to heed these warnings will result in one frustrated user due to lack of understanding.

btw, there is no need to run closed-loop. Just spend the time tuning your car properly and you will be better running open-loop so that the processor doesn't bog down with too many calculations and interrupt delays. Yes, MS will run closed-loop but it is not really necessary unless emissions are required.

At some point down the road you will discover that the motor needs internal attention. My breaking point was head studs. That's when I built the big cam, 3.2SS, twin-plug monster and matching short gear transmission. Yeah, IT ROCKS! Truly a spectacular sound at 7200 rpm.

[longhornchris04]

Jamie - thanks for the input. I'm hoping that by the time I'm ready to address cams I can afford the full rebuild (high compression 3.2 P&Cs + the reliability mods like those Dilvar studs). I'd rather not pay for a top-end build & cams twice (he says now...).

In the mean time (and there's a lot of it... market sucks but at least I've got a steady paycheck for the next 5 years) I'll get smart on tuning. I like the idea of EFI, especially DIY because I'm familiar with electronic controls (engineer by education). Any particular references you found most useful, besides the the MS forums and this board?

[MrPerkles]

Chris I went a similar route to Jamie who also gave me some good advice,he knows his stuff
I can tell you converting to EFI made the biggest difference to how my car felt and drove to anything I have previously changed
I am now rebuilding the engine due to a track mishap but the good thing is EFI is almost future proof and will compliment my planned mods.
Do your homework,read up before spending any money and it will be fairly straight forward to fit.
The throtle response from EFI is insane ,its not all about outright BHP