bripab007

Hmmm, sounds like there may have been something wrong with that old "Bonny." The MP62 'charger kits (and the 1.2L Whipple kits, as well) for Miatas all use bypass valves, and they make boost instantly and linearly. In those, the bypass' opening is constantly changing depending on the load/vacuum of the engine. So, for example, at 1/2 throttle, the bypass might be 1/2 open and at 3/4 throttle, with a decent load on the engine, it might be fully closed.

The end result is that they make boost nearly instantaneously, as long as the revs are high enough (say, above 2000 RPM, in the Miata's case).

dsmdriver

iTrader: (3)

Sorry- the only things we make have glass screens and update 64 times a second with whatever we want to put on them

But they do fit in a 3 1/8 hole. Or a 7" widescreen if you sit really far from the panel...

There's a reason that more homebuilts are registered per year in the US than mass manufactured planes. The homebuilts are much better in almost every way, including the price being hundreds of thousands less.

You didn't totally **** me off, but darting right in and telling me to stick something in my butt and then telling me that I'm lying about fuel effiency in an airplane isn't the best way to make friends.

I'll be at Reno this year. Maybe we can kiss and make up.

rotarygod

Good point dsm. I didn't take into account the physical properties as a vapor. It still isn't enough to power an engine though.

rotarygod

It was a little bit of an exaggeration to compare it to turbo lag but it is there. There is a split second where you can tell it takes the valve to close. It isn't much time but it is there nevertheless. It wasn't bad or even annoying. You could just tell that a bypass was present. When it closed you had full boost. Keep in mind I'm talking about a fraction of a second. Nothing to complain about.

rotarygod

Your engine rpm is tied to your speed. You can't just back of to a lower rpm and have the car still hold the same speed. Please don't get into automatic transmissions. Even they have their limits. If I need 3500 rpm to hold 70 mph, I'll need that regardless of how much pressure is in the intake. If I have 2 cars witht he same engine, one of them making 2 psi of boost and the other none, the one making boost will get worse mileage. Even if you had the exact same amount of fuel going into both engines, the one making boost is running leaner. You can only go so lean and still have the car run. If the car is shooting for stoich at cruise, that is more fuel for the boosted car. Even though it only takes a certain amount of power to hold a certain speed does not mean that you can't do it with more power. It's just a waste. There are many ways that you can waste the added power. One of them being in the form of heat.

dsmdriver

iTrader: (3)

RG, how does an engine decide to turn fuel into heat instead of into torque?

If the mixture is the same, more air means more fuel, and that means more power. The car *WILL* go faster. There's no valve or switch on the engine that says "turn this into heat instead of thrust." What happens is that your foot backs off the gas a little more to limit the air into the engine and thus back off the power to where you want it.

As I know very well from airplanes, manifold pressure means HP if you leave the mixture and RPM alone, which is what the RX8 does on the highway, shooting for stoich and cruising at a certian speed. So all we can adjust in the system is manifold pressure. Doesn't matter how the MP gets there- boost to 4289 PSI before the throttle plate for all I care- as long as the throttle plate offers enough restriction to keep the MP at 20", I'll produce the same HP at 20" of MP no matter how I get there. If I put the SC after the throttle plate- fine, the SC increases the pressure by 4" so I have to run 16" after the throttle plate to get 20" in the manifold. I do this by running less throttle position than I would if the SC wasn't there. This more closed throttle position equals higher pumping losses though, even if the MP is the same, since the SC is doing work to correct the higher restriction of the throttle plate.

The throttle does not equal RPM as your post seems to state. The throttle equals power. Your car cruises at a certian speed when power is equal to drag. If you up the manifold pressure, the power increases, and so does the car's speed. You must keep power the same to keep the speed the same (in the same gear, of course).

rotarygod

If your car can only hold any speed at any one rpm, how are you going to speed up if the engine doesn't or vice versa?

dsmdriver

iTrader: (3)

How are you not going to speed up if the engine produces more power due to the higher manifold pressure?

Produce more power means the drag is overcome, the car accelerates, the RPM goes up until the new speed's drag is equal to the new power level.

r0tor

iTrader: (1)

since no one mentioned the real key to water injection, it can increase the efficiency of an axial flow compressor from 85% to 115% (well if you flirt with wet compression)... its done in the power industry all the time.

The gas turbines can gain upwards of 15% power increase with not a whole lot of water being sprayed through the compressor (well, relative to the airflow anyway)

rotarygod

So what you are saying is that if we have 2 identical engines except one is making boost, at the same freeway speed, the one making boost (we'll say even 2 psi) must speed up and is incapable of holding the same speed because it is making more power? That IS what you are saying. That's wrong. Just because you only need to make so much power to go so fast does not mean that you can't make more power yet hold the same speed. Where are you measuring power? A supercharger boosting is a parasitic drag which means the engine must make more power to overcome it. You've got to at least make back the amount of power that it takes to create the boost. This uses more fuel and creates more heat. Don't think in terms of power to the ground. Think in terms of how much work the engine is actually doing.

As a crude example you might need 40 hp at the wheels and lose 10 to the drivetrain to hold a certain speed. If engine A is making 50 hp at the crank unsupercharged, it only uses the amount of fuel necessary for 50 hp. Again very crude example. Engine B also needs 40 hp at the wheels and also loses 10 hp to the drivetrain. However it's boosting supercharger may need 5 hp to spin since it is making boost. Engine B needs to make 55 hp to get 40 to the ground so it will consume fuel at a higher rate. Free spin the supercharger and it may only require a third of a horsepower to turn the blower. Fuel consumption goes back down. This is also ignoring any change in efficiency due to air temps. Now tell me how car B will speed up because it is making more power and tell me why car B won't be making more heat.

guitarjunkie28

*update*
i talked to scott today and he ran me through some basic stuff.

apparantly, the interceptor doesn't stage until manifold pressure reaches 1psi. unfortunately, it's running out of primary injector before the blower makes that amount of boost.

i talked richard into letting me steal the car for a few days next week. 2 thing i'd like to try are:

1) piggy-back p's and s1's. 4 primaries, 2 secondaries. that should take care of the problem, but i have to ask scott if it'll kill the injector drivers just to make sure.
or
2) just tell the computer it's running an rx7 and stage it at 5".

either way, wasn't enough time to fix the problem today, but i think we have it figured out.

Richard Paul

iTrader: (5)

You don't want to look at it from my side do ya? What if I added up how much I've got in this by now! How many people have to work on it so I can drive it?
Good thing I still have my Eldo to drive.

Now Guitar junkie wants to swap injectors around. Why do I have to do that?
I'm looking for input on this project, remember I'm to old to know anything but carbs and distributors. I've got Australia giving me input also.

It's not like I'm just playing around here, it's all costing money that has to be retrieved from the price of the SC kit.

guitarjunkie28

because the interceptor can't stage at that rpm unless it's in rx7 mode.

Richard Paul

iTrader: (5)

Staging is pulling up to the line at the dragstrip.

guitarjunkie28

OMG, you are older than dirt. lol

Richard Paul

iTrader: (5)

I was a juinor engineer on the team that invented cast iron.

rotarygod

Just think vacuum secondaries on a carb and you'll get the idea of what injector staging is.

Richard Paul

iTrader: (5)

Webers don't have those. But if I were running a Holley I have a box with a bunch of different colored springs so I can bring it in where I want.
I can see it and feel it. Then I can change the power valve to bring the fuel in when I want. If I modify it I can even chage the air corrector orfice.
If I really need to tune something out I can change the emulsion tune by shanging the fueling blocks.
Better yet I have some replacment fuel blocks that let you switch to Weber jetting. Then you can tune the **** out of it.

Do I have to tell you how great a distributor is? Or do you like this screwing around with all these burned up coils. With no sure fix in sight.


I can also make wooden spoke wheels for your covered wagon.
And buggy whips.

guitarjunkie28

would that spoke-wheeled wagon have an a/f on it?

california style

didnt this used to be a Supercharger thread?

Rootski

iTrader: (1)

I think by staging they mean activating the injectors in sequence.

Or were you being sarcastic?

guitarjunkie28

naw, he's just old. cut him some slack.

rotarygod

He invented sarcasm.

guitarjunkie28

i had to change his o2 sensor because i'm young and agile, but i'm gonna make him machine my rotors because he's old and skillful. 8.5 compression, here we come!!!!

now find me a 4-port motor so i don't have to spin those 9# slugs up past 8k.