911SC potential power?

[lateapex911]

I'm considering building a 911SC for SCCAs ITR class. Before I take the plunge, I need to determine what power the 3.0 can make under the rules.

The rules allow free exhaust, free aircleaner (but the intake tract must remain stock from the metering device to the engine, and all air must pass thru it) port matching is allowed 1"in either side of a gasket, and balance and blueprinting is allowed. Max compression is .5 over stock, (10.3/1) and the engine may be 40 over. ECU is open, and a MAP sensor may be added.
So, it's essentially stock, but tweaked a bit.

What are the major limitations to making power in that engine?

I'd appreciate any leads to someone who might be able to make an educated guess.

It will race against BMW E36 325s at 2850 pounds, and they put about 210 to 220 at the wheels. The 911 will weigh 2630 in race trim. I'm assuming that will be an easy number to hit with interior and door gutting, with a cage and a 200 pound driver.

Any advice, similar dyno numbers and thoughts are welcome!

[Joe Bob]

964 cams, headers and zoom tubes if noise is not an issue...

[lateapex911]

964 cams? Were they stock on any SC? If not, no dice. Headers ok, but whats a zoom tube?? noise is 101 dB at most tracks.

[Joe Bob]

ok....zoom tubes are straight exhaust.....you can try Supertrapps or maybe you can gut a banana muffler and make it into a sport muffler.

Cams...can you regrind? The SC cams are real soft due to smog restrictions. If you regrind to the "20/21" or 964 cam profile you can pick up 15-20hp.

BTW, stock euro 3.0s put out 210 ish HP.....25-30 hp more than the US models.

[cstreit]

Lots of thoughts here...

They say "balance and blueprinting is allowed" so if you really want to be a the top of your game, you'll find the lightest piston rods, pistons, etc.. engine components that Porsche made for the SC and target to those.

Your major limitation? The CIS, pistons, and cams. Not optimal. Exhaust noise limits leave you pretty open. That engine was about 180 stock right? 10.3:1 with the stock cams and CIS induction, dunno, maybe in the 200 range for easy updates. If you can use early heads with the bigger ports, bonus. Can you use alternative valve springs? If so, use them and go to 7000. I'd bet you could easily match the HP of the BMW's without spending too much coin.

[RaceProEngineer]

Jake,

There will be no problem achieving weight. In fact, you will have plenty of ballast to help balance corner weights.

We calculated 212+ HP at the flywheel on our "Stock" SC, limited to the sort of constraints you mention, and with the type of mods Chris has outlined. Balance and blueprint are basic. Raceware valve springs are a worthwhile investment. Free-breathing air cleaner, sucking the coolest air you can get to. Equal-length headers, coupled with straight pipes or megaphones paid huge dividends in throttle response. Sunoco 112 or similar race gas, and MSD Ignition and coil to ensure every drop is burned. Some sort of heat-exhausting vents in the engine compartment to keep temps as low as possible.

Being so restricted, you need to "find" an extra horse or two wherever you can. Then, as you already know, making the rest of the car MAXIMIZE its use of that limited power is the real "trick".

Ed LoPresti

[javadog]

I'd use an early engine as the basis ('78 or'79.) You can run the cams a little retarded and gain some on the top end. The late Euro SC made 204 DIN hp. at the crank. I'd say you might be lucky to get between 220 and 230 at the crank.

JR

[sfoster13]

Do you run PCA as well or will this only be an SCCA car? I looked into this as well and the turn off for me was that I couldn't run stock class in PCA with all the changes that I would need to make to the engine. I think you could get to the HP you're looking for if you start with the right engine. I'm assuming you can choose between the large port early US, the later US and the Euro engine. A couple of other things to keep in mind about IT (disclaimer - I don't run with SCCA but have done some research so take this with a big grain of salt). One is that you need to max the engine out to be competitive and that is not cheap with these cars ($15k??). Two, take a look at the weight allowances to the other Porsches. I haven't looked in a while but I remember them giving a weight advantage over the SC to the Boxster and the 944 S2 versus PCA weights which is crazy (meaning they get to lose more weight than the SC - not the final weights in absolute terms). IIRC the s2 and the boxster looked to be the cars to build for ITR. Double check the wheel/tire size restrictions. IIRC they are either stock or pretty close. That's going to make things a little more difficult even with the higher hp. These cars need rubber, especially in the back, and if you're running other series like NASA or PCA you'd end up with a lot of wheels. I have 3 sets for racing with NASA and PCA and would have to add another 2-3 in the right size for ITR. Let us know how you do, I'm curious to hear.

[lateapex911]

Originally Posted by mikez

ok....zoom tubes are straight exhaust.....you can try Supertrapps or maybe you can gut a banana muffler and make it into a sport muffler.

Cams...can you regrind? The SC cams are real soft due to smog restrictions. If you regrind to the "20/21" or 964 cam profile you can pick up 15-20hp.

BTW, stock euro 3.0s put out 210 ish HP.....25-30 hp more than the US models.

Wow great responses here.

Cams must be stock for the year on the spec line, so thats anything from 78 to 83 in this case. And euro parts aren't allowed unless they were stock on a car delivered by the factory in America.

[lateapex911]

Originally Posted by cstreit

Lots of thoughts here...

They say "balance and blueprinting is allowed" so if you really want to be a the top of your game, you'll find the lightest piston rods, pistons, etc.. engine components that Porsche made for the SC and target to those.

Your major limitation? The CIS, pistons, and cams. Not optimal. Exhaust noise limits leave you pretty open. That engine was about 180 stock right? 10.3:1 with the stock cams and CIS induction, dunno, maybe in the 200 range for easy updates. If you can use early heads with the bigger ports, bonus. Can you use alternative valve springs? If so, use them and go to 7000. I'd bet you could easily match the HP of the BMW's without spending too much coin.

yes, Chris, thats exactly what is done. find the best and match it. I've done it with an old street motor on my 2.4E,...spent nights with my grinder and scales, LOL.

If the "early" heads were from 78 -83, i am good to go. If not, no dice. Valve springs must be stock, OR replacement items that are the same material and dimensions as stock.

[lateapex911]

Originally Posted by RaceProEngineer

Jake,

There will be no problem achieving weight. In fact, you will have plenty of ballast to help balance corner weights.

We calculated 212+ HP at the flywheel on our "Stock" SC, limited to the sort of constraints you mention, and with the type of mods Chris has outlined. Balance and blueprint are basic. Raceware valve springs are a worthwhile investment. Free-breathing air cleaner, sucking the coolest air you can get to. Equal-length headers, coupled with straight pipes or megaphones paid huge dividends in throttle response. Sunoco 112 or similar race gas, and MSD Ignition and coil to ensure every drop is burned. Some sort of heat-exhausting vents in the engine compartment to keep temps as low as possible.

Being so restricted, you need to "find" an extra horse or two wherever you can. Then, as you already know, making the rest of the car MAXIMIZE its use of that limited power is the real "trick".

Ed LoPresti

Ed, thats good news on the weight. I suspected as much. I know that I'll be searching for the lowest drag wheel bearing grease and trans oil possible, LOL.

But, how much loss will the unit see, best case scenario? 15%???
In the end, it's a numbers game, power, braking and handling vs money!

[the]

Originally Posted by lateapex911

It will race against BMW E36 325s at 2850 pounds, and they put about 210 to 220 at the wheels.

Are the E36 325s really putting 210 to 220 at the wheels with just those tweeks?

Stock, I think they are around 190 at the crank. 220 at the wheels would calculate to around 260 at the crank. That's a 70 hp gain, and significantly more than the E36 M3 puts out.

[lateapex911]

Originally Posted by sfoster13

Do you run PCA as well or will this only be an SCCA car? I looked into this as well and the turn off for me was that I couldn't run stock class in PCA with all the changes that I would need to make to the engine. I think you could get to the HP you're looking for if you start with the right engine. I'm assuming you can choose between the large port early US, the later US and the Euro engine. A couple of other things to keep in mind about IT (disclaimer - I don't run with SCCA but have done some research so take this with a big grain of salt). One is that you need to max the engine out to be competitive and that is not cheap with these cars ($15k??). Two, take a look at the weight allowances to the other Porsches. I haven't looked in a while but I remember them giving a weight advantage over the SC to the Boxster and the 944 S2 versus PCA weights which is crazy (meaning they get to lose more weight than the SC - not the final weights in absolute terms). IIRC the s2 and the boxster looked to be the cars to build for ITR. Double check the wheel/tire size restrictions. IIRC they are either stock or pretty close. That's going to make things a little more difficult even with the higher hp. These cars need rubber, especially in the back, and if you're running other series like NASA or PCA you'd end up with a lot of wheels. I have 3 sets for racing with NASA and PCA and would have to add another 2-3 in the right size for ITR. Let us know how you do, I'm curious to hear.

Sfoster (sorry, i don't know your real name)..I'm actually on the SCCA ITAC (Improved Touring Advisory committee). I was the guy who actually made lots of phone calls and got an "ITR" sub committee formed, and then pushed it thru the ITAC and up the line thru the CRB and the BoD.

A few years ago, there was no process for clasing cars in IT. it was rtather hit and miss. A mess, frankly. A couple of us got involved and were able to convince the BoD (Thru a obscure rules wording) to allow adjustment to the IT category to get things in line and create parity. We had too many "one car" classes.

ITR uses the same process to clss cars. Essentially it takes stock power, a multiplier for IT gains, and a multiplier for the class performance envelope, and creates a race weight. Along the way there are adders and subtractors (we have a list of basic things like suspension type, drive layout, etc.) and the weights get fine tuned with those. We also do "sanity checks", like can this car REALLY lose the 1000 pounds it needs to weigh to be competitive in "X" class?". If not, it gets considered for another class.

Long story, sorry! In the end, the process isn't perfect, and it was never thought that it would be. IT entrants have expressed a strong desire for stable rules and weights. No "dickig" with things like the Prod guys do. And we need very well researched and well backed infor to move from the power estimate to a "known power in IT trim" in the calculations. We do estimate power differently for different engine genres, like rotaries vs DOHC 4 cylinders.

I have debated with the ITAC that the estimates are a little off when it comes to the 911s, as they are air cooled. i've made gains, but I'm still not sure we are where I'd lie us to be.

The 944S2, as you know, needs to weigh 2810 in race trim, the 911SC 2630. Both may run up to an 8.5" rim.

I actually purchased an S2 to build for ITR, but after looking carefully in the engine compartment. (Aaaaacccckkkk!) and talking with john Milledge (retired now) and determining that he would end up absorbing about $15K of my favorite dollars and THEN we'd talk ECU for another , um...$10K, I got cold feet and sold it. I considered a Boxster as well, but the buy in is pretty up there, and the weight is 2830. I do a lot of work to my race cars myself, including rebuilding my rotary and I've rebuilt 911s as well, so i'm most comfortable in a 911 engine compartment. I might be hung out to dry though, it might cost even more then an S2!

I would like to run mainly SCCA stuff, as I can run an easy dozen races well within a 5 hour tow, and can choose another dozen further away if I want. I would do some PCA stuff too, but as a "dessert" , and i wouldn't care if the car were "mis classed". I always hit the ARRCs as the last race of the year.

I realize that I need to look at other issues too, like suspension setup and cost, wheel fitment (must fit under stock but rolled fenders) and so on, but if the engine can't get in the ballpark, there's no point in trying.

[lateapex911]

Originally Posted by the

Are the E36 325s really putting 210 to 220 at the wheels with just those tweeks?

Stock, I think they are around 190 at the crank. 220 at the wheels would calculate to around 260 at the crank. That's a 70 hp gain, and significantly more than the E36 M3 puts out.

LOL, you've hit on a interesting point. We (the ITAC) had a huge issue with the E36s running in ITS. Stock examples were just pulling built examples of other cars like Zs and RX-7s (with known wheel power) like crazy down the straights. And not just one example of the BMW either...all across the country it was the same story.

So some research was done. I was able to convince an E36 owner to come and do a dyno run or 10...His engine wasn't a full build, but it put about 205 down at the wheels. And research turned up stock examples putting down 185 or 190 at the wheels. Automobile Mag did some dyno work as well, (web only, IIRC) and they found similar results. Certain BMWs are significantly under rated at the factory.

On top of that, the inline 6 sems to respond well to the tweaks and ECU mods allowed. They are very very stout. really good cars.

[groundeffect]

Hi Lateapex911,

I too am considering a ITR car and I had a couple of questions i hope you can answer...

In 1982 and 1983, the turbo rear wing was a factory option, is it legal?
Are 17" wheels legal on an SC?, (the 2008 GCR wording is a bit ambiguous).

Some thoughts on the formula...
I have been racing with NASA in their spec GTS class which is similar to ITR except that NASA mods allow about 250+ horsepower and 2400lbs with driver. I have been chewing up Carrera brakes in NASA and I fear at 2630 lbs for ITR, SC brakes won't survive. Also, raising the spindles is a fairly common mod on 911s, as I read the GCR, it is illegal.

Thanks for your thoughts.

[Eagledriver]

I don't see an SC competing with an E36 BMW. They're just too far apart in technology. Unless you cheat and cherry pick parts like Euro intake system, big ports from 78-79 and custom 96mm pistons and cylinders, you won't get the power you need.

-Andy

[rallyracer]

Originally Posted by groundeffect

Are 17" wheels legal on an SC?, (the 2008 GCR wording is a bit ambiguous).

Yes, 17" is legal. It's not really ambiguous, they just added the ITR clarification to the end of the paragraph. So, it's up to 17" or original diameter, if larger. If there is a size on the line specs (none for the sc), then that's your minimum diameter.

Other good questions of legality would be:
-pop off valves
-hydraulic chain tensioners

[lateapex911]

Originally Posted by groundeffect

Hi Lateapex911,

I too am considering a ITR car and I had a couple of questions i hope you can answer...

In 1982 and 1983, the turbo rear wing was a factory option, is it legal?
Are 17" wheels legal on an SC?, (the 2008 GCR wording is a bit ambiguous).

Some thoughts on the formula...
I have been racing with NASA in their spec GTS class which is similar to ITR except that NASA mods allow about 250+ horsepower and 2400lbs with driver. I have been chewing up Carrera brakes in NASA and I fear at 2630 lbs for ITR, SC brakes won't survive. Also, raising the spindles is a fairly common mod on 911s, as I read the GCR, it is illegal.

Thanks for your thoughts.

17" wheels are legal. I'd actually think about it in larger terms though, before jumping to 17"s. There may, or may not be cheaper wheels and tires in 16", and it's way of getting cheap gearing. Again, I haven't looked at the numbers though. But 17"s are an option.

So is the wing, but, if used, it must be the factory version. So, with the aero aid comes some weight. Not sure what the tradeoff is....

Moving spindles...Well, maybe. I'll have to look into that further. On my RX-7, we added spacers under the spindle. (Modified Ackerman in that way as well) Struts are free in IT, so it would seem that there is a way to mod the spindle height legally. I'm going to say yes, I'm 85% sure it would be possible to do in a legal manner.

On the brakes, air dams are free, so ducting is possible, and will be needed. On my RX-7 I replace discs pretty regularly...in the grand scheme of racing costs, it's pretty cheap. Proper cooling helps. But brakes must remain stock, with the exception of free pads, fluid, SS lines, backing plate removal and cooling.

[lateapex911]

Originally Posted by rallyracer

Yes, 17" is legal. It's not really ambiguous, they just added the ITR clarification to the end of the paragraph. So, it's up to 17" or original diameter, if larger. If there is a size on the line specs (none for the sc), then that's your minimum diameter.

Other good questions of legality would be:
-pop off valves
-hydraulic chain tensioners

yes, both of those are issues. I had thought the SCs had some form of Hyd. tensioner. If so, of course, those may be run. The pop off valves are clearly not legal.

Now, on both of those items, it would be VERY very weird and unusual for anyone to even object, and a protest would be a massive shock. They just aren't "performance enhancing" items that would anger a fellow competitor. Technically illegal though.

[rallyracer]

Originally Posted by lateapex911

yes, both of those are issues. I had thought the SCs had some form of Hyd. tensioner. If so, of course, those may be run. The pop off valves are clearly not legal.

Now, on both of those items, it would be VERY very weird and unusual for anyone to even object, and a protest would be a massive shock. They just aren't "performance enhancing" items that would anger a fellow competitor. Technically illegal though.

The Carrera tensioners that people put on 99% of the SCs were never available on an SC, and do not superceed the SC tensioners, so I'm betting on illegal, if the question were posed.