My Supercharged mx5 experience

[Mr nanotech]

So to those of you who know, I've taken one hell of a long time getting my supercharged na off the ground. I won't bore you with the details but in a nut shell I wanted to take a break from cars for a while and try some other hobbies, I took my time and plodded along bit by bit every now and then. Skipping forward a few months and I have an na6 with an m45 hot side supercharger running at 9psi with 550cc injectors and an intercooler. I'm using DIYPNP2 management and an LC-1 wideband.
As of now, the tune is still coming along and although not ideal, it's not running lean and although rich at times, not spitting fuel out the exhaust. I should also point out that before this, I had never dríven or been in a supercharged car.
My first impression was amazing, It was fun driving my mx5 suddenly with more torque down low and a cool new noise. I was very impressed with it and looked forward to refining it more and moving on to more serious tuning.
However, after a few more drives and taking it out today; my opinion has changed a little. I guess with more experience, my opinion has developed since my initial experience.

First off there are a few compromises that although I noticed initially, I have become more and more aware of each time I hit the road. The most obvious is the lack of throttle response. I'm not too sure if that is the right term to use, but because of the dual throttle bodies, there is a significant amount of pedal weight now which makes the throttle feel groggy and resistant. I suppose I could be more aggressive with my footwork but the car has definitely lost some of it's finesse in that area.
Secondly, the cut out on the supercharger. As you fly through the rev range, there is a point in which the superchargers power seems to trickle off and dwindle. I know this is par for the course from what I have read but sometimes it's like hitting a wall. This has lead to me decreasing the rev limit of the car to compensate.

(I have to leave now, so I'll continue this in another post)

[gslender]

Remove one of the two springs on each throttle body. Makes it feel like stock again.

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[Mr nanotech]

Thanks for the tip! I'll do that tomorrow.

I want to add that my experience with the supercharger has been largely positive before I go on further.

The next thing I'd like to mention is the power gains. I'm not 100% sure the timing is properly set up since I used an average timing light to adjust, which had a surprisingly dim lamp on it making it difficult to see the markers. I'm relatively happy with the power the car makes but I do feel that it seems quite under powered for what it is. Supposedly I'm running close to 10psi and have installed bigger injectors and standalone management. I expected a slightly larger pull from the engine, but once again this could be related to both timing and tune still. I'll work to correct this as time goes on.
Right now I'm having more fun with setting everything up, it's like playing with toys.

The last thing I'd like to mention is the sound. I've heard a lot of supercharged cars in videos and some in real life too, but none have been as loud as mine! I cannot hear the exhaust over the whine coming from the charger. It sounds great for the first few drives but the constant 'reeeeeeeeeeeeeeeeee' sound pinging in my ear gets a little old when cruising at a constant speed. I've been wondering if there are ways to lower the noise level or possibly sound deadening the underside of the bonnet and engine bay to eliminate some of the noise. Driving with the window down is very loud, so I can only imagine what it's like with the hard top down and no roof!!
This isn't necessarily a con or anything, but it was something I hadn't thought about prior to installing. There is one negative to the sound that is very apparent when driving though. The car makes so much noise that it's disproportionate to any gains felt by the supercharger, which makes it feel like the car is making a lot of noise but going nowhere.

[Mr nanotech]

Going back to power, there is one sensation I've noticed when ascending the rev range. In some ways it feels like the car has a very heavy flywheel. Dann explained this to me the other night as being a normal thing for superchargers, I'm not going into the technical speak because I don't want to get it wrong but perhaps he can further explain it in this thread.
I was wondering if a lighter flywheel might help with quicker spins and response of the charger maybe.

There are some questions I had regarding some of my experiences.

What can I do to combat some of the noise? It turns a LOT of heads when driving down the road (not in a good way)
Will a lightened flywheel benefit me?
What can I do to get some more pull from it?

[wozzah1975]

This topic is interesting.

I quickly googled the type of set up you have and noted a few things.

Firstly, because of the distance between your supercharger and your intake manifold and the length of all the intake plumbing the throttle response is always going to be less than ideal.

Secondly, when a supercharger reaches it's flow potential power drops off very rapidly (almost feels like to put the brakes on). What power your car is making will give me an indication on where yours would drop off, but that supercharger on a stdish 1.8 drops off rapidly from around 6200rpm onward. On a 1.6 it would probably be closer to 7000rpm.

Thirdly, throttle body size. This is an area where 99% of people over do it. Having the correct size throttle body for the given power output is a must for nice throttle response and drivability. What size are the twins?

And finally, have you had the car to a dyno for a tune to see exactly what it's up to? or just relying on a self tune? Do yourself a favour, get it tuned properly so you can see what's going on, and check the boost level accross the rev range.

I know what you mean about the feel of a supercharged car, they do feel odd at times. The engine is constantly under load, so part throlle driving feels very different. WOT should feel great though!!

Personally, unless you have to take the engine/gearbox out I wouldn't go to the trouble of lightening the flywheel. It will make it a litlle more responsive, but thats about it. It's something you would do if you were already in the process of carrying out other work and had it out.

Cheers
Woz

[Mr nanotech]

This topic is interesting.

I quickly googled the type of set up you have and noted a few things.

Firstly, because of the distance between your supercharger and your intake manifold and the length of all the intake plumbing the throttle response is always going to be less than ideal.

Yeah that did cross my mind. Since I have a front mount intercooler, the length of the piping between supercharger and manifold is quite a length. So in a way I'm not really surprised

Secondly, when a supercharger reaches it's flow potential power drops off very rapidly (almost feels like to put the brakes on). What power your car is making will give me an indication on where yours would drop off, but that supercharger on a stdish 1.8 drops off rapidly from around 6200rpm onward. On a 1.6 it would probably be closer to 7000rpm.

Ah that makes sense! That's the sensation I have been experiencing, it really feels quite dramatic on WOT. Keep in mind that my supercharger is spinning at twice the standard speed as it has a reduction pulley to increase boost roughly 9-10psi. The standard boost level on one of these is approximately 5psi. I'm guessing this could be why on my 1.6 the supercharger feels like it's hitting it's flow potential roughly around 6500rpm

Thirdly, throttle body size. This is an area where 99% of people over do it. Having the correct size throttle body for the given power output is a must for nice throttle response and drivability. What size are the twins?

I'm still using the standard na6 throttle body on the intake manifold, however I have a nb8b throttle body on the supercharger as this has a larger diameter if I recall correctly.

And finally, have you had the car to a dyno for a tune to see exactly what it's up to? or just relying on a self tune? Do yourself a favour, get it tuned properly so you can see what's going on, and check the boost level accross the rev range.

Not as of yet, I'm slowly self tuning and refining it bit by bit. Dyno is definitely on the cards, but unfortunately I have money tied up right now in house renovations, buying a car for my sister and finalising holiday booking for mid January. When I have the money to spend, it will hit the dyno as soon as possible.

I know what you mean about the feel of a supercharged car, they do feel odd at times. The engine is constantly under load, so part throlle driving feels very different. WOT should feel great though!!

Yeah it's a very different feel to turbo and not what I'm used to at all. In a lot of ways it makes the car feel like it's got a bigger normal aspirated motor in it. Like a 2L or something. More punch to it but all linear.

Personally, unless you have to take the engine/gearbox out I wouldn't go to the trouble of lightening the flywheel. It will make it a litlle more responsive, but thats about it. It's something you would do if you were already in the process of carrying out other work and had it out.

I had the opportunity to do this a while back and after some research (at the time) I opted out. I had a super light Toda flywheel to go in the car but I was researching and stumbled accross a few articles about superchargers benefiting from a stock flywheel the same way some bigger block engines do. The theory was that down low it took more force to spin, but with enough power (ie supercharger or big block engine) you could ride the momentum of the car throwing the heavier flywheel. I don't know how much of that is true, I'm not into physics. But in hindsight it seems like something that worked on paper but not practical in the real world.

Cheers
Woz

Thanks a lot for the help mate. I don't know if you remember but we met a while ago when John Pham was picking up his head from you. You did an amazing job on that by the way. Appreciate the advice.

[93_Clubman]

Secondly, when a supercharger reaches it's flow potential power drops off very rapidly (almost feels like to put the brakes on). What power your car is making will give me an indication on where yours would drop off, but that supercharger on a stdish 1.8 drops off rapidly from around 6200rpm onward. On a 1.6 it would probably be closer to 7000rpm.

Ah that makes sense! That's the sensation I have been experiencing, it really feels quite dramatic on WOT. Keep in mind that my supercharger is spinning at twice the standard speed as it has a reduction pulley to increase boost roughly 9-10psi. The standard boost level on one of these is approximately 5psi. I'm guessing this could be why on my 1.6 the supercharger feels like it's hitting it's flow potential roughly around 6500rpm

Not sure which pullies you're running for approx 9psi, but if you've not seen it here's TDR pulley RPM (motor & SC) chart:
http://trackdogracing.com/pulley_rpm.aspx

[Garry]

I drove the first of the supercharged JCW Mini's and I wasn't impressed with supercharger technology compared to turbo's. I'd heard a lot of talk of the instant throttle response of supercharging vs turbo's but the Mini didn't feel any more responsive than my MX5 in the lower rev ranges. It felt like it hit a brick wall around 5000rpm. It stopped making power and was just making noise, whereas the MX5 makes power pretty much all the way to the redline. And the whine of the supercharger was painful. I was well and truly over the noise by the end of the test drive. I can barely hear the turbo in the MX5. Maybe the Mini installation wasn't a good one but it has turned me off supercharging. BMW must have thought the same thing switching to turbocharging for the current Mini.

[NitroDann]

Try to name a single currently supercharged available model that isnt supercharged for tradition (ie a mustang or something)

Even the mini is now turbocharged.

Fact of the matter is that lowering compression on turbo setups isnt very common anymore, and the result is that response and revviness is the same between a stock car and its aftermarket turbo version.

Compare this to a blower which is directly connected to the crank weighs a lot (like a big flywheel), and a HUGE volume of air between the throttles and the engine throttle response is just not that amazing, the idea comes from big blocks with 6/71's and when you have 9L's and 10psi of boost on cross ply tyres. Touch the throttle and you can shred them. Thats hp, not response.

Dann

[wozzah1975]

Try to name a single currently supercharged available model that isnt supercharged for tradition (ie a mustang or something)

Even the mini is now turbocharged.

Fact of the matter is that lowering compression on turbo setups isnt very common anymore, and the result is that response and revviness is the same between a stock car and its aftermarket turbo version.

Compare this to a blower which is directly connected to the crank weighs a lot (like a big flywheel), and a HUGE volume of air between the throttles and the engine throttle response is just not that amazing, the idea comes from big blocks with 6/71's and when you have 9L's and 10psi of boost on cross ply tyres. Touch the throttle and you can shred them. Thats hp, not response.

Dann

Hi Dann,

If the supercharger is mounted where it should be (on a plenum on the inlet side, the same as what you would do a V8) and it is executed correctly (no long piping or intercooler) the throttle response and instant power is still much better than a turbo set up. The issue is that alot of newer style supercharger kits are set up like the above, long plumbing and in some cases through an intercooler. It defeats the purpose of using a supercharger to begin with. My theory is that you either set up a supecharger properly, or like you said turbo it instead.

Cheers,
Woz

[wozzah1975]

This topic is interesting.

I quickly googled the type of set up you have and noted a few things.

Firstly, because of the distance between your supercharger and your intake manifold and the length of all the intake plumbing the throttle response is always going to be less than ideal.

Yeah that did cross my mind. Since I have a front mount intercooler, the length of the piping between supercharger and manifold is quite a length. So in a way I'm not really surprised

Secondly, when a supercharger reaches it's flow potential power drops off very rapidly (almost feels like to put the brakes on). What power your car is making will give me an indication on where yours would drop off, but that supercharger on a stdish 1.8 drops off rapidly from around 6200rpm onward. On a 1.6 it would probably be closer to 7000rpm.

Ah that makes sense! That's the sensation I have been experiencing, it really feels quite dramatic on WOT. Keep in mind that my supercharger is spinning at twice the standard speed as it has a reduction pulley to increase boost roughly 9-10psi. The standard boost level on one of these is approximately 5psi. I'm guessing this could be why on my 1.6 the supercharger feels like it's hitting it's flow potential roughly around 6500rpm

Thirdly, throttle body size. This is an area where 99% of people over do it. Having the correct size throttle body for the given power output is a must for nice throttle response and drivability. What size are the twins?

I'm still using the standard na6 throttle body on the intake manifold, however I have a nb8b throttle body on the supercharger as this has a larger diameter if I recall correctly.

And finally, have you had the car to a dyno for a tune to see exactly what it's up to? or just relying on a self tune? Do yourself a favour, get it tuned properly so you can see what's going on, and check the boost level accross the rev range.

Not as of yet, I'm slowly self tuning and refining it bit by bit. Dyno is definitely on the cards, but unfortunately I have money tied up right now in house renovations, buying a car for my sister and finalising holiday booking for mid January. When I have the money to spend, it will hit the dyno as soon as possible.

I know what you mean about the feel of a supercharged car, they do feel odd at times. The engine is constantly under load, so part throlle driving feels very different. WOT should feel great though!!

Yeah it's a very different feel to turbo and not what I'm used to at all. In a lot of ways it makes the car feel like it's got a bigger normal aspirated motor in it. Like a 2L or something. More punch to it but all linear.

Personally, unless you have to take the engine/gearbox out I wouldn't go to the trouble of lightening the flywheel. It will make it a litlle more responsive, but thats about it. It's something you would do if you were already in the process of carrying out other work and had it out.

I had the opportunity to do this a while back and after some research (at the time) I opted out. I had a super light Toda flywheel to go in the car but I was researching and stumbled accross a few articles about superchargers benefiting from a stock flywheel the same way some bigger block engines do. The theory was that down low it took more force to spin, but with enough power (ie supercharger or big block engine) you could ride the momentum of the car throwing the heavier flywheel. I don't know how much of that is true, I'm not into physics. But in hindsight it seems like something that worked on paper but not practical in the real world.

Cheers
Woz

Thanks a lot for the help mate. I don't know if you remember but we met a while ago when John Pham was picking up his head from you. You did an amazing job on that by the way. Appreciate the advice.

Hi Mate,

I do remember meeting you. Cheers, glad John was happy with the job

[wozzah1975]

Secondly, when a supercharger reaches it's flow potential power drops off very rapidly (almost feels like to put the brakes on). What power your car is making will give me an indication on where yours would drop off, but that supercharger on a stdish 1.8 drops off rapidly from around 6200rpm onward. On a 1.6 it would probably be closer to 7000rpm.

Ah that makes sense! That's the sensation I have been experiencing, it really feels quite dramatic on WOT. Keep in mind that my supercharger is spinning at twice the standard speed as it has a reduction pulley to increase boost roughly 9-10psi. The standard boost level on one of these is approximately 5psi. I'm guessing this could be why on my 1.6 the supercharger feels like it's hitting it's flow potential roughly around 6500rpm

Not sure which pullies you're running for approx 9psi, but if you've not seen it here's TDR pulley RPM (motor & SC) chart:
http://trackdogracing.com/pulley_rpm.aspx

That chart is a bit basic, and I wouldn't pay too much attention to the rated engine RPM figures. I'm not a fan of using smaller blowers and overdriving heaps to get them to make power, it creates unwanted intake charge heat, and in most cases you end up with a situation of the blower simply running out of air which is an unpleasant feeling. Once a supercharger reaches its flow potential in doesn't matter how much faster you turn it, it won't pass anymore air. You're far better off picking a power figure, then getting a blower to suit. That way there is no need to run an intercooler and the power delivery is much better an more controlled.

Cheers
Woz

[NitroDann]

But then you have no cooling, less power, less efficiency, so you have to make a much better setup than an equivalent turbo setup.

Dann

[wozzah1975]

But then you have no cooling, less power, less efficiency, so you have to make a much better setup than an equivalent turbo setup.

Dann

The only thing more efficient with a cooler is thermal. Everything else is actually a step backwards.

My argument is that the way this kit is done, an many other current set ups, it takes away any bonus of a supercharged car over a turbo car. If the blower has to be mounted so far away, and it needs to be cooled because it is undersized and over dríven you may as well just turbo it (we are in agreement here I beleive!), as it will still suffer the same lack of throttle response and lag to a degree. In some cases intercooling is more a problem than a benefit depending on what you want, especially in situations where heat soak isn't an issue.

If I ever get the chance Dann I will take you for a ride in a properly supercharged car. There is no substitute for the instant power and torque a decent set up delivers. The fastest 1/4 mile cars even today are still supercharged.

Granted, with current technologies turbo cars are much better than they ever used to be.

Cheers,
Woz

[Dweezle]

Sorry to sidetrack this thread for a moment but wozz's post reminds me of a question I keep meaning to ask.
Those ginormous V8s with superchargers sticking out through the bonnet., (think fast&furious charger), how do they get away without coolers??

Is it just due to the supercharger not being too small and spinning slower so as to create less heat?

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