Gonna be on the track next week

This is for a 73 T with a recently-added 3.6 liter engine, and some other mods.

Tracquest's thing is on Monday. I've got some questions.

First, I got the correct old-style sender to go with my numeric gauge. I don't yet have a fan or shroud for my Carrera cooler, and I've been getting readings in the 180-210 range in spirited street driving, with ambient temp of 65 degrees.

I know this is going to get hotter on the track. Is 250 my 'everybody out of the pool' moment, where I pull over and let the engine cool?

Also, regarding sender-gauge matching, my oil pressure readings seem higher with the new engine (just as the sender-gauge mismatch made the temps seem cooler, initially). It rarely drops below 40 on the gauge, hits 100 under mild acceleration, and climbs to about 120 above 3000 rpms. Is this acceptable? Do I need to replace the 1993 sender with one designed for the 1973 gauge?

Also, I finally got the sway bars on, front and back. Both are 22mm. Weltmeister in back, and AJ-USA's through-the-body replacement set-up in front. Both are adjustable. Any tips on good initial settings for these things? Driving it on curvy local roads, I most notice the understeer when I'm accelerating. On a tight curve, if I lean into the pedal, it's like a big hand pushes me from behind, and toward the outside of my turn. I'm not breaking the front tires loose, but it seems the car is pretty content to plow right over them.

Tomorrow, I'm putting on 7-inch wheels in front and 8-inch wheels in back (with 225s and 245s), which should improve the grip (not that I've really tested the limit of the current wheels yet). Any advice on tire pressures or other ways (with the sway bars) to get this thing ready for the big track at Willow Springs?

Thanks for any guidance.

And by the way, this double-your-horsepower thing rocks.

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Jack Olsen
1973 911 T sunroof coupe

[This message has been edited by JackOlsen (edited 10-25-2000).]

Sounds like fun, Jack!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 10-26-2000).]

Jack,

It sounds like you need the '73 oil pressure sender. I don't quite understand why every Porsche made since electric gauges were initiated couldn't have used the same sender, but they don't! As far as the 'bail-out' temperature under load, I think 240 F would be safer, since it does not take long at all to get from 240-250 F under load and you might not be able to keep a very close eye on it! Bruce Anderson said high temps idling or lightly loaded doesn't cause damage the way it can under full load ... I am certain you don't want to be taking any risk of serious damage on your first outing, so I would recommend prudence in the matter! Remember, Bruce Anderson's 'comfort zone' is 180-220 F!!!

As far as the anti-roll bar settings go, it sounds like you have a bit of strong understeer with your current settings! Do you have both adjusters out at 'max' length, or minimum force setting? If so, you may want to move the rear adjuster a little closer to the bar center by an inch or so. If that doesn't get to 'neutral' steering rather than pushing, try another inch closer to the bar center on the rear. If you get too much oversteer at any point, move the front adjuster closer to center in half-inch increments ... the front adjustment is a little more 'sensitive' so move it less each time.

As far as tire pressures go, try starting at 32 psi front and rear, cold. Chalk your tire side walls with 4 vertical/radial markings equally spaced around the periphery of all four tires, starting at the flat part of the tread and extending 2" toward the axle, 'up' the sidewall. After a few practice laps, check the chalk marks to see if worn away at the intersection of tread and sidewall ... if chalk is worn away extending out or up any on the sidewall, more pressure is needed in that tire. And, remember, pressures increase with higher temps, and the cold 32 psi will rise 2-5 psi when hot.

One final caution -- the first lap after any 'adjustment' in anti-roll bar or tire pressure should be taken very carefully! I know you don't want any scratches on 'Black Beauty' on the first outing!

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Warren Hall
1973 911S Targa

There are two books that help enormously on setting up suspension. But both are at home and I'm not. I will take a stab at the names and allow someone else to get the correct info. Here are the guesses on names.

"The Art of Solo II Driving" Very popular book and well know author whose name is ?????. Should be in any Barnes & Noble book. Great section on adjusting sway bars.

"How to Make Your Car Handle". The rest is foggy. Long time since I read the books.

The net result of these books is to do the seemingly illogical thing. For a push, you tighten the rear and loosen the front. For oversteer you tighten the front and loosen the rear. The correct logic is to stiffen the end of the car away from the problem thereby decreasing the weight transferred by longitudinal twisting of the car.
It works.
David

As far as the oil pressure issue, you might also check that the engine ground strap is in good condition. The sender gets its ground from the engine which gets its ground from the chassis.If the engine isn't adequately grounded to the chassis, you will get higher than normal readings. I've experienced this firsthand with a corroded ground strap. The 3.6 has a much larger pressure pump in relation to the scavenge pump than your original 2.2l did, but those readings still seem pretty high provided that's with a fully warm engine. Did the shop that did the conversion remember to reinstall the strap? Or it may have not been there in the first place since you bought it. Check at the nose of the trans. There should be a copper braided strap between the firewall and the nose of the trans. Also, try this. With the engine running run a jumper wire between the engine and a good chassis ground and watch for fluctuation at the guage. If not then its probably mismatched sender and guage like Warren said. BTW. Idle oil pressure is going to be higher on the 3.6 than the 2.2 because of the aforementioned pump differences but not as high as your current readings.

A quick update: the car handled great today on the track. Oil temperatures were no problem at all. I put together an aluminum scoop that drew air up the front side of the oil cooler (into the fender) and then used aluminum pieces to seal off around the cooler so that the rammed-in air would have no route out other than through the cooler. Temperatures rarely got above 210, and -- on some of the later runs -- got up to about 230. Considering I was in the 130 neighborhood at two different points on the track, that seems pretty good. Of course, it was in the sixties out in the desert, so there may still be work for me in the summer.

But she's cool for now, which is cool.

I had Steve Alarcon at Suspension Specialties/Johnson Alignment set up the sway bars and do an alignment and balancing. With less gas in the tank, the car weighs in at less than 2500 pounds, which was nice to learn.

The 225 tires (Bridgestone Potenza RE71s) would not even come close to fitting in my 1973 fenders, which was odd. I rolled one fender's lip before trying the first tire (one small paint chip, now fixed -- but I was prepared for worse), but the problem was with the tire's overall diameter (225/50 16), which meant it connected with the front spoiler and front inside of the fender. I guess each car is unique.

I'm now planning on getting a pair of Potenzas in the 205/55 size for the 7-inch wheels, but it also occured to me to try another brand in the less-common 215/50 size. That would be slightly wider, and slightly smaller in diameter than the 205/55. Any opinions?

The car was very fast and very precise. It's finally a car that reveals my limitations as a driver (as opposed to its limitations as a "t"). But that just means I need to take it out more...

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Jack Olsen
1973 911 T sunroof coupe

[This message has been edited by JackOlsen (edited 10-30-2000).]

Very glad to hear the car handled well and had no oil temp problems!

About the front tires, how about 225/5-ZR-15's on 15 x 7 Fuchs? The 15's would have 1/2" more clearance (1" less OD, 1/2" less radius and MORE clearance) and would have more footprint area than 215/50-16's!

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Warren Hall
1973 911S Targa