Supercharging fact and fiction help me clear up my worries

[schmeky]

ThatSilver Car,

Hate to tell you this but if you go with a PD blower you are definitely not going to have instant torque off idle. Not even close.

So just be aware of this before you spend the money and take the plunge.

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[ThatSilverCar]

ThatSilver Car,

Hate to tell you this but if you go with a PD blower you are definitely not going to have instant torque off idle. Not even close.

So just be aware of this before you spend the money and take the plunge.

I'm not sure how to accomplish it, but I really wish I could drive both PD and centrifugal with a manual. A. To see if I like it so much I have to have it regardless or risk. B. Which feels better to my preference.

Not sure who'd let me drive their car cause I know I wouldn't let someone drive mine.

Seems like anecdotally all of this is all over the place.

 

[robvas]

ThatSilver Car,

Hate to tell you this but if you go with a PD blower you are definitely not going to have instant torque off idle. Not even close.

So just be aware of this before you spend the money and take the plunge.

Don't listen to this guy.

Yes, you will.

 

[schmeky]

If you go 50 - 75% throttle off idle you will have instant torque. But not in normal driving.

 

[robvas]

If you go 50 - 75% throttle off idle you will have instant torque. But not in normal driving.

Doesn't that contradict what you just said:

Hate to tell you this but if you go with a PD blower you are definitely not going to have instant torque off idle. Not even close.

Are you correlating 'idle' with throttle position or RPM? No supercharger or turbocharger will go into boost at lower throttle positions. You have to go close to WOT to do that.

Most people would consider 'off idle' flooring it from a low RPM situation, say just idling along at 3-4mph in 1st gear (or no throttle in 2nd or 3rd gear, letting the engine idle speed just carry you)

 

[HKusp]

Don't listen to this guy.

Yes, you will.

Listen to THIS guy. If you go PD blower with good tuning, you will have an abundance of low end torque with some throttle. On street tires, MT82 car (even drag radials), with good tuning, you will be hard pressed to get good traction at over half-3/4's throttle in 1st, 2nd and 3rd gear. If you get someone to tune it with torque by gear, you can manipulate that, but basic tuning you'll blow the tires away in 1st and 2nd above 3/4 throttle. It becomes an exercise in throttle control, in a good way if you know how to do it.

 

[barron64]

I have not done a track day yet but...I have 1000mi of day to day driving, using the A/C when needed, along with a few runs up into the mountain curves, on my new Whipple/VMP Gen 6 stg 3 install. All I can say is Wow! What a compliment to a 6sp GT PP1. Those long gears with the MT-82D4, are not so long anymore. Those 6 piston Brembo's finally get some real use now. Will it run hot on a 30 min track day session? Possibly, but it is totally worth it on the street. Best mod I have ever done to the car.

 

[fiveoboy01]

But I worry that adding boost is going to remove my ability to ever track my car again without doing some heavy engine work either before or well... after .

Well, it basically will, without the supporting mods. Mainly cooling.

You'll want to ditch the factory cats for extended track work too. Overheat and melt them, and you run a pretty high risk of damaging the engine.

Street car? Go nuts. I have had no issues in about 10K miles(I have a centrifugal setup) of street and autocross use. It is a lot of fun to drive.

There are plusses and minuses to each type of blower. I think the linear delivery of a centrifugal blower is more suitable for street use and limited traction scenarios.

 

[NightmareMoon]

Yeah this thread is all over the place.

If I had to pick a blower, gimme turbos. PD second. Centri 3rd and great for a straight line car.

For track NA because you arent going to get fast trying to be fast in 2 laps and sitting the rest of the session out waiting for the motor to cool off.

 

[Johnny Ringo]

Listen to THIS guy. If you go PD blower with good tuning, you will have an abundance of low end torque with some throttle. On street tires, MT82 car (even drag radials), with good tuning, you will be hard pressed to get good traction at over half-3/4's throttle in 1st, 2nd and 3rd gear. If you get someone to tune it with torque by gear, you can manipulate that, but basic tuning you'll blow the tires away in 1st and 2nd above 3/4 throttle. It becomes an exercise in throttle control, in a good way if you know how to do it.

^ This 100%. If I whack my throttle in 2nd or 3rd gear just cruising at "idle" it'll hit boost instantly and blow the tires off immediately. You absolutely have to modulate your way to full throttle, and even then there are no guarantees once you get there until around 4th gear.

 

[Pistol_91]

Yeah this thread is all over the place.

If I had to pick a blower, gimme turbos. PD second. Centri 3rd and great for a straight line car.

For track NA because you arent going to get fast trying to be fast in 2 laps and sitting the rest of the session out waiting for the motor to cool off.

Yep... Racing on the track is a lot similar to motorcycle racing. All the noobs think you need 9000hp to have fun or be fast and neglect the massive fact that being fast is mostly the rider/driver. Power helps but modern vehicles have enough power to not matter anymore.

You make a great point. I'd rather be on the track ringing out my 350hp car as fast as possible rather than waiting for my 800hp car to cool down.

 

[mejohn50]

This is the second thread in recent weeks where there's a debate about low end torque on PD superchargers. This discussion is wild because people apparently don't quite understand how this works.

The amount of throttle pedal input is more or less irrelevent because tuners can change how much torque is requested for a given pedal input at a given RPM. This can make a PD car feel stock depending on conditions.

If a tuner sets a car up to request nearly stock torque values at 2000 rpm and ~10% throttle pedal, it doesn't matter how much boost the supercharger can make, it will only request stock torque values from the engine, which will make the car feel...stock.

Here is an example. My stock 2019 Mustang GT auto driver demand table (top) and the stage 2 Whipple driver demand table (bottom). You can see in low pedal input ranges, it more or less requests stock, or nearly stock, torque values. This means it will feel more or less stock. If the values were increased in the low pedal input areas to request more torque, then it will feel more powerful. You can see in this example that it doesn't start meaningfully requesting more torque until into the high 30% to low 40% pedal input range.

That is why we are seeing this feedback that it requires substantial pedal input to make the car feel like it has a supercharger strapped to it. It's 100% the tune, and tuners can make it feel any way they want. If you want your PD car to feel stronger down low, ask your tuner to change it so it feels how you want it to feel.

 

[robvas]

It's the amount of engine vacuum you are pulling. Because the bypass will be open and you won't make any boost.

So when someone says pedal being pushed down they are talking about the throttle blade being open. No matter what your throttle controller or tune are doing to goof with those values.

 

[mejohn50]

It's the amount of engine vacuum you are pulling. Because the bypass will be open and you won't make any boost.

So when someone says pedal being pushed down they are talking about the throttle blade being open. No matter what your throttle controller or tune are doing to goof with those values.

A pedal value, through a series of events, is translated into a throttle body opening, but it isn't natively a throttle body opening (10% pedal doesn't necessarily equal 10% TB opening) and it can also vary based on RPM. The throttle body only opens enough to allow enough air to create the requested torque value that is called up in the driver demand table for a given throttle pedal percentage and engine RPM. The driver demand table dictates the torque request, and the torque request at a pedal input and engine RPM dictates the feel. A tuner could set the driver demand table to request 500tq at 2000rpm and 10% throttle pedal...bet a dollar it gets into boost if setup like that.

 

[engineermike]

Yea, even the stock gt500 tune iirc calls for stock gt torque levels up to something like 50% pedal and….that’s what you get. I personally like my supercharged engine to “act” more like a 10 or 12 liter engine so I have it hitting you with a lot of torque in the first half of pedal travel. That’s just my preference though.

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