[Frit]

In the tbirds case its a regular FPR that maintains the equivalent of 39psi at all times. Essentially, if your making 15psi of boost, you'll see 54psi on the rail to maintain the 39.

Stock wise the sc's heads and exhaust flow very poorly. Just dropping the resonator will drop you about 2 to 3 psi right there, so generally you start OD'ing the blower to get the 2 to 3 psi back which amounts to more power. The problem of course is that OD'ing the blower will increase your ACT's very quickly.

Unfortunately we are stuck with just the heads we have with only porting work done on them as no one has ever made aftermarket heads for our cars.

In these cars as auto's, you've generally maxed out 42# injectors at around 280 rwhp as they would be running close to 100% duty cycle, and the 5spds can usually get to almost 300rwhp. Right now my car is estimated at around 240-250 rwhp and I'm seeing about 82% inj duty cycle with the 42's.

[stanger007]

First off, the V6 will always need larger injectors than a V8 to produce the same amount of hp since there MUST be more air going into the V6 cylinders as compared to the V8. Likewise, an L4 will need larger injectors than a V6 to produce the same output.

My buddy runs 72lb injectors on his turbo 4cyl import to crank out around 350hp. When we first started the build, I thought he was way oversized on the injector but after doing the math, it is right on.

Wes

[patrickmx2]

I see what you mean and this topic came up with me and a friend of mine this morning on a road trip to Alabama (visit to meet some friends at PTC -Performance Torque Converters so it was all car talk all day). This guy has 4 Buicks, 3 T-Types and one Grand National. He mentioned how restrictive those engines intakes and heads are from the factory (by todays standards). He was making 30psi of boost and 450hp. Needless to say that is a turbo application, not a supercharged one so the load on the crank isn't there but it is very hard on head gaskets at that boost level. That's still an insane power level from a 3.8 cid motor that is mostly stock internals. In this case though you are right about the FMU being a hack because their injectors were not 60lbs but what he did have would have been undersized because his answer was that he doesn't care much for FMU's either and since he acquired the car with this hardware he is making changes to get rid of problems inherent to running an FMU like you describe.

That said I can see where it would be easier for a Buick to generate 450hp since there is no loss going to power the supercharger being a turbo car.

[cgrey8]

Some people argue that turbos are easier on the motor than superchargers because they don't have the parasitic load like superchargers do. I tend to disagree. They are probably easier on the motor and the load they put on the motor is likely a lot lower, but turbos do have a parasitic load.

In any motor, the exhaust gas is under considerable pressure. That's what creates the power during the power stroke. But just because the piston has reached the bottom of the power stroke doesn't mean the exhaust is no longer under pressure. It's still under considerable pressure. When the exhaust valve opens, the exhaust gases release themselves from the chamber for the most part. So most of the work in expelling the exhaust is done before the exhaust piston moves upward for the exhaust stroke. The piston pushing up is just pushing the final amounts of exhaust out, but the amount of exhaust pushed out on the up-stroke of the piston isn't nearly as great as the initial release of exhaust when the valve begins to open at which point the piston is actually still moving downward. With ported exhaust ports, aftermarket heads with bigger valves, or a performance cam, the exhaust gas can release itself even faster which further reduces the resistance the piston experiences on the exhaust stroke. The less resistance the exhausting piston experiences on the upward travel of the exhaust stroke, the more power that gets out the end of the crank.

With a turbo in the mix, the turbo relies on that fast release of exhaust as the valve opens to spin the impeller and produce boost. The side-effect is this dramatically slows down the rate at which the exhaust frees itself from the chamber...way more than small valves and restrictive exhaust ports. This means there is a much higher PSI of exhaust gas on top of the piston as it travels up for the exhaust stroke that is going to require power...the parasitic load. So the parasitic load from a turbo isn't on the end of the crank, but is on each piston's exhaust stroke. The less restrictive the heads on the exhaust side, the more exhaust PSI hits the impeller. The lower the PSI on the intake side, the less resistance the exhausting pistons have to overcome. The less restrictive the intake system is, the lower the PSI for the same amount of air going into the motor.

Point being anytime you are dealing with forced induction systems, higher performance intake and heads are even more important to overall engine efficiency because the performance of one component directly affects other parts. Big surprise....it takes money to make performance. Nothing comes for free in engine performance. What else is new?

[Frit]

You have a point about Turbo's and SC's. Each has its strong points and its weakness.

Since I can only talk for the blower side of things, think of it this way. to drive the M90 Eaton's blower at around 15000 rpm's (thats slightly overdriving) your looking at 80 HP coming off the crank to do that. Now picture doing the same thing with 25% OD and your easily talking 130HP coming off the crank to drive that sucker.

With that in mind, if the tbird is making 450rwhp, and you take about 20% drive train loss because of the auto and you take the 130hp to drive the blower.... your talking 670hp at the crank being produced out of that little 6 banger .

It amazes me cause I've always thought you'd need a V8 to make any power... Unfortunately its the only way the V6 is going to make that kind of power.. it will need help either by SC or turbo, or nitrous. Speaking of NOX, we have some guys tesing how much a stock bottom end can handle for nitrous and so far I believe they have got to a 250 shot.... and blew the AOD :? on the dyno. The AOD is actually a built up version for our cars.

We have some guys building duel turbo setups, and a couple of guys doing a combo SC and tubo setup. The blower kills us once we get over 5200 RPM's. The motors themselves can easily hit 7000 RPM"s, but the blower won't let us, so the idea is to use the roots blower down low to get the beast moving, then transfer over to a turbo as the REV's build up.

One guy has built a 1.7L AR kit to fit our cars, and these guys are low 11's now if they have their motor built for the higher RPM's. There is talk now about going to a 2.2L AR kit.... essentially, we haven't hit the limit what these motors can do with stock bottom ends.... its too scary.

The cars are almost 19 years old and it looks like we're just now getting our stride to what these motors can do. We have guys that have pulled the 5.0's out of their stangs and dropped the SC 3.8 motor in, and completely stock motors these stangs are pulling low 13's. Of course they have to replace the stock tranny's because these motors will even blow those things apart on the first WOT run. I've heard about the big name TKO tranny's getting blasted apart. The 5spd we have in our cars are from the F150 pickup (M5R2) and it can barely hold up, but again, we can't get replacement parts for those. These motors are laying down over 300 ft lbs of torque at 2400 RPM's at the wheels stock.

This is one of the reasons I'm here, as I want to see what these cars(motors) can really do, and the more I learn about the EEC the more I feel I can give to the guys to reach those goals. We have to deal with a situation where there is very little aftermarket support for our cars, and getting parts a VERY expensive . We have to pay almost $400 for a BHJ harmonic balancer, and its the only option we have over stock.

The Grand National is an amazing car in itself (and man If I can afford one I'd be all over it.. especially a GNX), and it is often used as a comparison to the TBird SC... but the cars a 2 different beasts. While the GN might beat the SC on the drag strip... put it on a twisty road race somewhere and the SC will have it for breakfast. The SC weighs around 4000lbs, but with its suspension and its ride control system can out turn alot of big name performance cars, including the Mustang, and include alot of european performance cars. The SC was designed to run with the Beamers and Merc's etc on the Autobahn at 140mph all day long... and she can do it easily while getting 20+ mpg.

It also has been proven that the TBird SC is much more aerodynamically efficient than any Mustang ever built. The club has pretty much determined from Ford folks that the TBird SC was way better than the Pony car at the time so they actually detuned the EEC, and put exhaust etc modifications in place to hurt the TBird so it wouldn't sell as good . The biggest thing about all of this, was the TBird SC was the test bed for Ford to use the super charger on its regular production vehicles as well as alot of other computerized features like ABS, Ride Control Suspension etc on everyday production vehicles.... and they don't even acknowledge the SC even exits anymore.

Anyways, all I'm doing is bragging about the rare TBird SC so I'll step back now. I'm a proud owner of an SC and the club estimates there is only about 35000 left in the world in good shape... if that.

Also, the club has the only ford researched AWD SC ever built, and we're in the process of restoring it. Its full of Porche parts for the AWD system. Alot of us are thinking what would it be like to have all that bottom end torque with an AWD system .

Sorry for being long winded. I'm just a proud owner of a very rare unrecognized car LOL!

[Jack Hidley]

cgrey8,

Since your profile says you're an engineer, you probably realize this, but maybe not:)

There are two reasons not mentioned so far, that make turbos more efficient than superchargers.

1) The power to drive a supercharger has gone through one more conversion process than in a turbo.

2) Once blowdown in the cylinder occurs, there is significant energy still in the exhaust gas in heat/pressure. The actual cylinder pressure during blowdown evacuates the cylinder much more than you think. It is easy to imagine the cylinder pushing out the exhaust gas, but in reality this process is very nonlinear. IE. most of the exhaust gas has left the cylinder when the piston is still near BDC due to the heat/pressure, not the piston motion. The increase in exhaust pumping losses are not linear with BMEP. There is only a small increase in pumping loss for a large increase in BMEP.

"Internal Combustion Engine Fundamentals" by Heywood has some very good explanations and data describing this.

[cgrey8]

I most definitely agree that this blowdown is a very non-linear event with or without a turbo.

I also agree the scavenging of the blowdown energy is MUCH greater than the parasitic load put on the motor to expel the exhaust gas on the exhaust stroke. It's this reason alone that the turbo is able to make boost and gain engine HP. I also agree that this scavenging of exhaust blowdown does make the turbo more efficient than a supercharger making a turbo the ideal inductor...at least IMO.

I don't think any of this is in debate.

What I'm not convinced of is that a turbo can make a gasoline engine more efficient (not more powerful) than a naturally aspirated motor. A turbo DOES make a diesel motor more efficient because intake of air is NOT related to diesel consumption, so scavenging the exhaust blowdown energy and turning that into boost most definitely improves both efficiency and performance. However, I've just never heard of anybody claim a fuel economy increase by installing a turbo to a stock gasoline engine and realize a fuel economy increase.

Notice that I focus on fuel economy since fuel economy is in direct relation with engine efficiency. If fuel economy suffers due to the existence of a turbo, you must have a parasitic load you are feeding.

Does that make more sense?

The one thing I am curious about is if a turbo motor's Brake Specific Fuel Consumption (BSFC) value measures lower than that of a supercharged engine since there is some energy scavenging with the turbo?

[Frit]

it looks like the GURE has PRLDSW = 0... which means I need to go find that setting

Try address 0x98B0.

EDIT: amended 0x98B1 to 0x98B0

Hey Bob,

I was digging further into the GURE code and we where both originally right, 0x98B1 is the switch. I was thrown off as I thought I was logging the right locations for LOAD and LOADX, and they "appeared" scaled from each other. Turns out LOADX was actually LOAD, and I found the location for LOADX as well.

This has also shown me why I need to scale everything down. In its current state, the car easily goes over 160% load. If it wasn't scaled down, I would be breaking the 200% limit for load.

ps- As a side note I need to get an update to Clint for BE for GURE.