Tires, Wheels, And Rotating Mass - Question

"Master Cylinder" (mastercylinder28) 08/08/2015 at 20:32 • Filed to: None

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I’ve got two sets of wheels for my 944 that I’m in the process of refinishing. I’m nearly done with the last pair, so I’m starting to think about how I want to use them.

The wheels are “Cup IIs” from a 993, and they come in a staggered set of 17x7 and 17x9. My original plan was to use a square setup with 245-series summer tires mounted on the four 17x9 wheels, and mount 215-series snow tires on the 17x7 wheels.

Then I decided to toss the wheels on my scale and discovered that there’s a whopping 10-pound difference between the 17x7 and 17x9s. So mounting the 17x9s will be an increase of 40 pounds of rotating mass to a car that’s already pretty low on power.

On the other hand, it’s a 944, it’s never going to be that fast - it’s all about the handling anyway, right? Plus, big fat tires always look sweet.

I do still have the original 15” wheels that I could use for winter duty, run 17x7s all around, and sell off the 17x9s.

Anyway, I guess the question is - what would you do, Oppo - narrow but light wheels or wide but heavy wheels? I suppose I could split the difference and run them as a staggered set, but that seems kind of pointless on a low-powered car with a near 50:50 weight distribution.

K-Roll-PorscheTamer > Master Cylinder 08/08/2015 at 20:45

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Wait, you have a 944 too?

Master Cylinder > K-Roll-PorscheTamer 08/08/2015 at 20:57

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:)

OPPOsaurus WRX > Master Cylinder 08/08/2015 at 21:11

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finish them, sell them, and buy something you want

K-Roll-PorscheTamer > Master Cylinder 08/08/2015 at 21:15

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Year? Miles? When? How? Wut? Wut Are you doing with said car?

HOW’D YOU FIND A WHITE ONE???

Master Cylinder > K-Roll-PorscheTamer 08/08/2015 at 21:53

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It’s an ‘87 S, about 200,000 miles (estimated, the odo was broken when I bought it and I drove it for a few months before I repaired the odo). I’ve had it about a year and a half now, still catching up on deferred maintenance.

My goal for the car is a semi-stripped lightweight street build, kind of RS or Clubsport-style. I’m aiming to drop the weight to 2500 pounds and to bump the power up to as close to 200 rwhp as I can get without spending a huge fortune. First, though, I’ve got to finish catching up on all the deferred maintenance from the past owners.

I’ve rebuilt the front suspension, did the timing belt/water pump/front engine seals, new Koni yellows all around, swapped out the leaky power steering for a manual rack, rebuilt the AOS and vacuum system, all coolant lines - basically I’m replacing everything that’s made of rubber.

I know of another white one that’s going to be up for sale soon - my dad has an ‘84 that he was building up as a project but he recently bought a Boxster S instead. I’ll be helping him prep it for sale, it should be on the market in 2-3 weeks.

K-Roll-PorscheTamer > Master Cylinder 08/08/2015 at 22:00

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You and me both, mines in the shop as we speak....I have the strange feeling that you already know that, and my memory is rubbish. Wanted an S, but I hear limited parts and that lot is an issue at times, so the 8v is good enough for me!

That sounds like a most awesome idea. How do you plan on removing that much weight from the car?? I’d love to make a 944 RS. 200rwhp?? What are your plans to do that?

Sounds like you’re on a roll so far. How difficult doing the vacuum system? You’re smarter than I am, replacing all the rubber bits right away.

Dammit! I would have loved a white ‘84! All they have in Michigan are red ones, I kid you not. You’ll be pressed to find a 944 that isn’t red, black, or silver.

Master Cylinder > K-Roll-PorscheTamer 08/08/2015 at 22:20

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2500 lb is my goal, but I’d be OK if I can get to 2600 lb. I know some folks have gotten them down to 2100 lb or so, but that’s a stripped-out racer. I think that going to fiberglass for the hood and bumpers, lightening the interior, ditching the uber-heavy stock exhaust, and dumping the unnecessary extras should be enough to get to 2600 lb. Finding that last 100 lb might be a struggle, though.

The S starts out with about 190 hp at the crank, so getting to 200rwhp isn’t as much of a stretch as it is with the 8v cars - a header, MAF conversion, exhaust, and maybe cams should be enough to get close. I’ve thought of a V8 swap but I actually really like the Porsche motor. Maybe if it blows up...

K-Roll-PorscheTamer > Master Cylinder 08/08/2015 at 22:49

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Apparently the curb weight for stock 1984 944 is 2800lbs. It’d be awesome if I could somehow shed even 1-200lbs while keeping most of the amenities I’d want, and that includes the full interior and heat/AC. I guess if you follow the idea that every ounce counts, you could take bits from just about everywhere to make it add up.

How heavy is the stock exhaust anyways? I know these cars don’t really sound good with aftermarket exhausts, that’d be the one personal problem I’d have.

I’m starting with 143, god only knows what kinda mods I’d have to make to the engine to even get to 200rwhp, or even 175rwhp.

Master Cylinder > K-Roll-PorscheTamer 08/08/2015 at 23:08

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Yeah, the exhaust is a problem. I bought the car with a hacked-up exhaust and it sounded like shit. The stock exhaust sounds fine but it is really heavy.

And yeah, weight reduction is all about making the little things add up. There are a few of big-ticket items you can do (FG hood, bumpers, fenders, ditch A/C, strip interior, etc) but after that you’re looking at losing a pound or two here and there to get the rest. Some of that weight loss can cost $$$$$, too. I plan to keep A/C and heat, but otherwise losing a lot from the interior. The useless rear seat weighs about 20-30 pounds and costs nothing to remove. I’ve read that the carpet and sound deadening weighs about 75-80 pounds just by itself. The power seats weigh about 60 pounds each, so swapping in manual seats can save a good chunk of weight. It’s a lot of work but it’s far easier to drop weight on a 944 than to add power!

K-Roll-PorscheTamer > Master Cylinder 08/08/2015 at 23:39

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If only there was some way to retain the stock sound and create a lighter exhaust.

I probably wouldn’t(read as can’t) go fiberglass things like hood, bumpers, and the whole lot, but removing things here and there from the car would be ideal. That’s crazy about the carpet and sound deadening though! Doesn’t it contribute to rust protection to an extent? I’ve also got the manual sports seats so there’s that.

That’s the bloody problem/curse of these cars, especially the 8v cars. You simply cannot add power in a cost effective and efficient way. I just don’t understand why?? You can do it with almost any other Porsche engine, save for the 924 2.0L motor.

Master Cylinder > K-Roll-PorscheTamer 08/09/2015 at 11:46

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After I get the boring but necessary maintenance stuff done, the exhaust is my first project. I think it’s possible to lighten it while still keeping the sound reasonable. The problem is it’s a fairly big 4-cylinder, so it makes an exaggerated 4-cylinder sound, which isn’t always good. Right around 3000 RPM and again around 4000 RPM there is a resonance that really makes an awful, tinny, fart-can sound. That’s the main problem. After fixing the hacked-up exhaust that the PO put on, and before going back to stock, I had a setup that sounded awesome below 3000 RPM but just sounded like trash above. It was probably a good 15-20lbs lighter than stock, too. My plan is to run a high-flow cat, a BIG resonator, and then a reasonably-sized muffler. The muffler is where most of the weight savings will come in, I think - the stocker is just gargantuan. I think the key is getting the resonator right - you have to dampen those resonance points or it’ll sound like a 16-year old’s Honda. It’ll still be louder than, stock, though.

I think the sound deadening is probably the opposite of rust protection - when it gets wet it just stays wet for a long time. Besides, there’s a ton of undercoat and the sheet metal is galvanized. Fortunately, rust isn’t a big worry on these cars. The manual sport seats +rails come in at 35 lbs each (I have a set that I’ve weighed), so they’re reasonably light, but if you wanted to lay out some cash for really lightweight seats, you could save another 20-30 pounds there, as well. I thought about that but it’s a lot of money to spend and those seats are just so comfortable it’s worth the slight weight penalty, IMO.

And yeah, it’s frustrating that there aren’t really any easy bolt-ons that give big gains. A good header + exhaust is only worth 7-10 hp at most on the NA, switching to a MAF setup gets you maybe 10-15hp, a hot cam can net another 10 or so... after that, there’s not much left unless you open up the engine, and that gets bloody expensive quick.

From what I’ve read, the main reason that it’s so tough to add more power is that Porsche already did a pretty good job of squeezing as much out of the motor as it could from the factory. When you consider that the 2.5L is basically half of a 928 motor, which only made about 220hp when it first came out, it’s kind of impressive that they were able to get 163 hp (out of the non-US models) out of the 4-cylinder.

K-Roll-PorscheTamer > Master Cylinder 08/09/2015 at 12:33

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That’s exactly it!! Those fart sounds at 3000 and 4000rpm are what kills it. Everything else sounds just fine. I never even thought 2.5L out of a 4-cylinder was even that big. When you finish that exhaust, I’d love to give it a listen, and then maybe copy you if it’s a cheap endeavour. :p

I’d personally keep the carpet, but the sound deadening must be the majority of that weight. And knowing Porsche, it’ll probably be a PITA to remove. How do you plan on tackling that adventure? Could probably get behind the dash and remove some unnecessary wires and whatnot too; perhaps even simplify some things.

MAF setup is the most confusing thing to me. How does it work? What exactly is the difference between stock AFM and MAF? Why not Megasquirt instead?

And that’s the unfortunate good point you bring up. If only they followed through with that inline 5, V6, or even 2.7L V8 they had planned for their 989 sedan....

Master Cylinder > K-Roll-PorscheTamer 08/09/2015 at 14:13

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Yeah, the majority of the weight is likely in the padding and sound deadening. There’s no trick to getting thr sound deadening off, unfortunately. I’ve done it on a couple of cars and it’s just a lot of scraping. I’ve heard dry ice can help break it up though.

There’s a company called appbiz that sells a lightweight Perlon carpetkit, and you can have them make it “RS” style, meaning they give you carpet to cover where the rear seat was. I may do that or I may give it a go from scratch. I’ll use some Dynamat or similar around the wheel wells to help damp road noise but overall I am expecting about 30lb of reduction from that, plus my carpets are trashed anyway so it’ll be an aesthetic upgrade too.

I just refer to MAF conversion as a general term for ditching the barn-door AFM. I plan to run Megasquirt which will actually be a MAP setup instead of MAF. But there are vendors that sell MAF conversions that work with the stock DME and don’t require a standalone ECU, too.