Improving "Street Performance" With Bolt-Ons

[hoss4659]

I define "street performance" as increases in low and mid-range torque output with accompanying more immediate throttle response and better acceleration. Because I am driving an '88 911 my interest is focused on DME equipped cars.

Lots of threads and dyno tests point to enhanced street performance from exhaust modifications coupled with a Steve Wong custom chip. I will take that as a given, a necessary first step. What, if anything, might be done with the induction side? A couple of questions come to mind. First, would there be a benefit from replacing the "barn door" mass air flow sensor with a less restrictive hot wire or hot film type sensor? Might require some chip changes to maximize results. Second, there is probably a track performance benefit to be gained with a increasing the throttle body bore. How far down the rev range would this extend? 5000 RPM? 4000 RPM? Or is it likely to negatively effect the low and mid range performance? Again, some chip tuning would probably be needed to maximize the benefits. If you have dyno test results to share, they would be appreciated.

[midnight911]

Steve's chip will get you nice torque curve improvements. But if I were you, i'd rather go with exhaust, cut out air box for better noise. Refresh suspension components, brakes, and tires to get the handling back, and just drive it all day long. Perhaps invest more in driving skills via autox, track days, etc. Performance may mean different things for different people, but these cars are not about hp or merely going faster. To me, my 911 is an instrument I play with. Just my opinion, ignore at will.

[Quicksilver]

Porsche didn't screw up with our cars. They didn't leave anything on the plate with the 3.2 besides swapping the exhaust for headers. Other then headers, you can spend a lot of money to make more noise but it won't get you anything on the dyno.

Your choices are: compress the intake charge with a turbo or supercharger, open the motor up and spend a lot of money to make it bigger or spin faster, or make the car weigh less.

[Pstallo]

I agree with the Steve Wong chip, airbox, and exhaust (I use an M&K cat bypass) for street performance. And by street performance, I mean 'seat of the pants' feeling and sound.

I don't know that it significantly affects top-end speed or horsepower, but it feels like it must move the power curve lower down the RPM range where it's more accessible during regular driving. It just feels more sporty if that makes sense.

[jpnovak]

You really want Sal's MAF conversion for throttle response and more torque. Get rid of the obstructions in the airflow path before the throttle body.

[stlrj]

In my search for my Carrera I drove quite a few and found that not all are created equal as far as low end power. All were stock as far as I could tell, yet some were very quick while others were very disappointing.

The one I finally chose was mediocre at best until I tried a spare air flow meter and the difference was night and day. It put some snap on the bottom end to the point where I often took off in 2nd without giving it much thought and rarely revd much higher than 2500 around town.

To put it into perspective, I have 3 air flow meters and they all have different personalities just like the different Carreras I tested in my search.

I hope you find success in the low end performance that you are looking for as you will find it totally intoxicating and worth the search.

Sal Carceller seems to have an excellent system that might be what you're looking for.



Cheers,

Joe

[mysocal911]

Originally Posted by Quicksilver

Porsche didn't screw up with our cars. They didn't leave anything on the plate with the 3.2 besides swapping the exhaust for headers. Other then headers, you can spend a lot of money to make more noise but it won't get you anything on the dyno.

Your choices are: compress the intake charge with a turbo or supercharger, open the motor up and spend a lot of money to make it bigger or spin faster, or make the car weigh less.

That's the only realistic post in the thread!

[Nick Triesch]

Old 911's like the 3.2 are endurance cars, not 0-60 cars. You would be better off getting a 2012 + ford mustang 5.0 for super torque. Soccer Mom cars have 300 H.P. now! Ordinary pick up trucks have 300+ H.P. now.

[Nick Triesch]

And if you spend a lot of money to make it louder all you will get is a car that sounds like a really loud 67 Bug.

[mreid]

The big three: Flow improvement, weight reduction, traction gain.

[manbridge 74]

I'd buy a new Camry....

[Quicksilver]

Power isn't the point in a 911.

The point is that a 911 can outrun a higher powered car because halfway through the corner a 911 can be on the power when other cars are just getting off the brakes. Everything in a 911 is usable.
That is the difference.

[Nick Triesch]

Maybe 30 years ago. Or in a newer 911. The new high powered cars are great in curves, brakes, 0-60 and 0-100. It is true that our cars are fun in the turns but today's cars have so much power that they will lose us on a nice straightaway. And we can never catch up.

[DRACO A5OG]

Originally Posted by mreid

The big three: Flow improvement, weight reduction, traction gain.

+1 & 911Chip.

[DG624]

I modified my 3.2L '86 Carrera and got over 250 HP (215 RWHP) by modifying the intake with Extrude Hone (matched to the TB and intake) and Steve Wong chip with CAT by pass M&K. I have not had a dyno since the intake improvements but there should be more. I also had the injectors cleaned and tested by Marren.

Sal Carceller seems to have an excellent system that might be what you're looking for.

I have not investigated the MAF.

[gliding_serpent]

Originally Posted by hoss4659

I define "street performance" as increases in low and mid-range torque output with accompanying more immediate throttle response and better acceleration. Because I am driving an '88 911 my interest is focused on DME equipped cars.

Lots of threads and dyno tests point to enhanced street performance from exhaust modifications coupled with a Steve Wong custom chip. I will take that as a given, a necessary first step. What, if anything, might be done with the induction side? A couple of questions come to mind. First, would there be a benefit from replacing the "barn door" mass air flow sensor with a less restrictive hot wire or hot film type sensor? Might require some chip changes to maximize results. Second, there is probably a track performance benefit to be gained with a increasing the throttle body bore. How far down the rev range would this extend? 5000 RPM? 4000 RPM? Or is it likely to negatively effect the low and mid range performance? Again, some chip tuning would probably be needed to maximize the benefits. If you have dyno test results to share, they would be appreciated.

I am late in the game here, but have been thinking and reading a lot about this topic for over a year now. I am no expert, but I hope to be objective. Take what I say with a grain of salt.

What if anything might be done on the induction side?

This is a complex question. If you are staying close to stock hp, your gains are limited. A steve wong chip, a cat bypass, and a sport muffler should get you around 240 crank hp. If you look at Steve Wong's site and browse his dyno charts, you will find cars with the stock intake system running near 290hp. Folks say the AFM is good to flowing 12,00CFM before it becomes overly restricted. at 90-93% volumetric efficiency at 6200rpm, that is good for about 283hp based on my calculations. That jives with what SW sees on the dyno.

Now, air is not an on off switch like that, but my point is that more intake flow can help, but the benefits pay off more in engines that draw in more air (make more power) thus stressing the limitations of the stock intake's flow capabilities. A 3.2 at 240hp may make 1-2 hp with an enlarged throttle body (measurement error?) but I bet that 290hp engine that is trying to suck the sheets off of your bed would kill for one... and any other intake mod you could give it. I bet it would get over 300hp easy with a few easy intake mods.

Would there be a benefit from replacing the barn door AFM with a hot wire/hot film type sensor?

In addition to what I said above, remember, the 964's 3.6 uses the same AFM as the 3.2. Mind you, that engine makes 250hp stock. Assuming an optimal AFM function (and temp, altitude, etc, sensors), and a quality MAF, all else being similar, there should be no obvious difference under typical situations. A MAF is superior for accuracy, and thus why modern cars use them. That helps emissions, and it helps response. In my mind, with increased accuracy comes reduced fluctuation around target AFR's (too lean, and to a lesser degree, too rich and you lose power)... the less you engine varies from the target AFR, the safer is is, and the less power/efficiency you lose. You achieve that with measuring accuracy, but it is doubtful to be huge as far as seat in your pants... maybe a bit more throttle response.

But, all else being equal, on a dyno you will probably not show you that difference. Now, if you MAF is less restrictive than the stock AFM (larger cross sectional area), or it is hooked up to a well designed cone filter, and your engine is air hungry... than that will give performance gains, with increasing returns in engines that need more air (make more power). It is like a bigger straw to breath through.

Benefits of a throttle body bore? How far down the rev range would this extend?

As noted above, for a 240hp engine... probably not much gain, if any. A well known guy who sells them admitted the same (he said maybe 1-2hp in a typical modded 3.2). Mind you, throttle body increase from 63 to 66mm seems like very little, but actually increases the cross sectional area by ~10%. So you just increase the flow capacity of your tb by 10%. Again, an increasingly more useful thing if your engine is making more and more power (higher intake needs).

In summary, an engine is an air pump. It adds fuel to air to make power. The more air in, the more fuel you can add, the more power you can get. So if you want more power you have four basic options: (forced induction aside)

1. get more air into and out of the engine. you do this via intake mods,exhaust mods, comp ratio, afr's, cams, injectors, piston design, ignition timing, helmholtz resonance, etc. Gets quite complex when you really dig in. You are basically doing everything you can to make your engine have a better volumetric efficiency (take in more air than it should based on displacement).

2. Increase the combustion efficiency of the engine: Overlap with a lot of the above. Better injector spray patterns may also help, but the stock injectors do fine at near full tilt. Modern ones might do better at lower pulse frequencies.

3. Reduce internal mechanical losses. Our cars are estimated to lose about 15% to drivetrain losses. Lowering rotating mass (light flywheels, clutch, crank, rods, pistons, lighter wheels, etc) and rotating resistance (knife edging your crank) makes your engine waste less energy on spinning itself, allowing more of it to be put to the road. Down side is that rpms will sink like a rock if you go too light, resulting in increasingly challenging drivability. This is the hot car that stalls at the stop light if you are not careful, or that lugs on the track because you did not rev match properly when shifting up and took too much time shifting.

4. Remove real world limitations that Porsche had to design into their engines. Tuning a car for power is easy. All you care about is power and driveability. Most folks can give you that. Bonus is that with power can come better fuel economy/emissions when you are not on it (because you increased combustion efficiency). Factory engineers however need to engineer things like emissions, fuel economy, noise pollution, long term reliability, and cost in addition to drivability and power. As such, power can take a hit. Tuners simplify the equation and thus can usually get a bit more power out of a car by changing ECU code, even with everything else being unchanged. The more things like noise and emissions (and $$$ for parts) you are willing to sacrifice, the more power you can get.

As a final note, a good tuner will advise you that step one to a more powerful car, is to make sure it is working properly in the original form. No use tuning around a problem.

My advice is pick a budget and go from there. For enough money, youf car can see over 300hp. For that money you can also buy a faster modern mustang.

If it were me and my 3.2 were solid, for usable power I would go with a cat bypass, a SW or Cal C. chip, a sport muffler, and I would open up my airbox. That is the low hanging fruit and would make for a fun reliable 3.2 that would not break the bank.

When your car eventually needs a top end, I would look into 964 or 20/21 cams. They are doable on the street. Next time you need a clutch, get something a bit lighter like a KEP or a aluminum Sachs. Ever need new pistons?... 3.4's are cheaper assuming you don't go wild with twin plugs. And if you do go twin plug, bump up your compression ratio and do hotter cams while you are at it to get the best bang for your invested buck.

If your AFM is warn out, or you are getting into a car with high power/intake needs, think about a MAF with a cone intake filter, enlarged TB, extrude honed intakes. If your injectors are on their last legs, consider referbs, or Sal C's chip solution that uses modern injectors. Way cheaper than new original ones.

Exhaust: for a lightly modded street 3.2, I would get SSI's if you have the money, cat bypass for the original system if you do not. For a more moderately to heavily modded car (over 250hp), go back to stock heat exchangers or something of similar size with equal length primaries as you will benefit from the larger primaries. Don't get too fussed over header design beyond primary diameter and length unless you start getting into aggressive high overlap cams.

Yikes... that is sounding expensive. It is.

Finally, remember that the car is only as good as the driver, and adding lightness is as good as adding power. Ditch the spare tire, get a lighter powersport battery (when yours meets its end), ditch the rear seats (you can bolt them in as needed), and get rid of the AC (did it really work? If it does I bet a lot of $$ was sunk into it), and you have saved ~150lbs, which is worth about 15hp!!! That is free power (new battery aside, but you needed to replace it anyway).

Good luck.

[gliding_serpent]

Originally Posted by DG624

I modified my 3.2L '86 Carrera and got over 250 HP (215 RWHP) by modifying the intake with Extrude Hone (matched to the TB and intake) and Steve Wong chip with CAT by pass M&K. I have not had a dyno since the intake improvements but there should be more. I also had the injectors cleaned and tested by Marren.

Sal Carceller seems to have an excellent system that might be what you're looking for.

I have not investigated the MAF.

I will PM you in case you are not subscribed. Did you have your AFM/TB flow tested prior to extrude honing? And then did you get them to flow match each plenum to the values you got from the AFM/TB? Would you care to share your flow data? I ask because it would save me money testing my TB, and I am just curious. If you have a flow curve I would LOVE to see it.