Supercharged cars have lag too. In fact all cars have lag. "turbo lag" should more appropriately be called "fuel lag". It is the delay time that exists between when you press the gas down and the engine actually starts to rev. The slower and easier you drive the less you notice it. Just sit still sometime and press and release the gas pedal really quick. Different cars respond a little differently but I can actually get my foot back off the gas before the engine starts to rev (in both of my cars). It isn't something I notice driving though. When a turbo starts to spool, it does it pretty quickly. A car with a turbo like a nonturbo car may have lag, but at least they get to enjoy a surge of power when the turbo really gets going. A centrifugal supercharger has the same lag as the engine does stock but doesn't build up boost as fast as a good turbo system (or a bad one for that matter). Power is added at an exponential rate to rpm and with a peak boost level of say 8 psi at max rpm vs a turbo at 8 psi, the supercharged car is much more lethargic. The other thing popular today is the positive displacement supercharger such as the roots or twin screw. These typically have a bypass valve that opens under light load for economy reasons. When you step on the gas there still isn't any boost for a while. The bypass valve has to sense the difference in intake manifold pressure. The throttle has to have been pushed down and air already flowing down the runners for this to occur and that takes time. Then the valve has to close and the air boosted from the supercharger has to make it's way down the intake manifold to the engine. A turbo system also has to have air flow a long distance before it gets to the engine so each system is relatively comparable in terms of "lag". A positive displacement supercharger adds another complication in that typically the throttlebody is placed in front of the supercharger. This isn't disastrous but the farther the throttlebody is from the engine, the greater the lag time and slower the initial response. My turbo RX-7 which has a big streetport and big single IHI turbo puts out about 425 hp and has LESS lag time then my friends factory supercharged Pontiac Grand Prix. When done properly, "turbo lag" is nothing more than a myth. If you were to use an overly large turbo that is sized way too large for the engine then you would get a bad lag since boost would never rise. If a small turbo spools quickly, how do we have to wait for it to build up boost? If you mean to reach max boost then maybe but remember that max boost on some superchargers is also max rpm. a small turbo responds so fast that the rise is damn near instantaneous. Cars that have the least amount of lag time will either be carburated since fuel and air are mixed at the same time relatively close to the engine, or a fuel injected car that has the throttleplates close to the engine such as a BMW M3. There is almost nothing instantaneous about a supercharger unless you have a blown top fuel funny car. I see a benefit to each setup but "lag" is a nonissue on a turbo car. If it is an issue, the system wasn't designed properly or you just don't need the benefits of any type of forced induction.

 

I got a headache reading that. More paragraphs would be cool. But eitherway I disagree. I always thought my FD didn't have any lag. Once I drove the rx-8 I realized that my FD has alot of lag. Infact, under 2500 RPM my rx8 has more torque. How sad is that.

 

Yeah I should have seperated that a little better. You sure your FD was running right? The RX-8 will have more torque than the FD when the FD isn't under boost. My friend Trixie's FD is using the stock turbos in sequential mode and that thing reponds very fast. It also has a PowerFC which made it much smoother than stock. Like I said my big streetport single turbo 1st gen has less lag than my friends supercharged Grand Prix. This still doesn't change the fact that every engine has "lag".

 

I still have my FD, yes its running right. IT has a new engine ported with 3mm seals built by rx7fasion.com (ricks rotary). Im in the area of 330-340 rwhp. the first turbo is spooled by a bout 2600 RPM or so.

I have the power fc, water injection, fuel pump, injectors, intercooler, etc. actually I have everything save a single turbo.
I know the FD has less lag that most turbo cars, but im just saying its not the same as n/a.

 

Reason I asked was because there are so many people who own FD's that aren't working properly. Sounds like you've got a nice one. Actually it sounds like you got 2 nice cars.

I never said there wasn't any difference in lag times. You yourself admitted you thought the response was very fast on that car but that it is just faster on the RX-8. That's probably true but also consider that the RX-8 has a higher compression ratio and an induction system that gives higher intake velocity to the engine at almost all rpms. This will help out with response incredibly. Add a turbo to this and it will probably still be very nice.

My comments are aimed at the people who associate a turbo with severe lag and a loss of driveability especially in regards to a supercharger. This just isn't true if designed properly for street use. A big drag car that has a very peaky powerband and huge turbo would be a handful but remember that they leave the line at a high rpm and utilize some other form of help to get them off the line under high boost. They don't need throttle response. They need all or nothing.

Looking back I'm not quite sure what I typed that you disagree with. I never said lag may not be different. I just said that it isn't a big problem that everyone thinks it is and then stated how other forms may be just as bad.

I made several little paragraphs. Happy?

 

OK as for the update.

Supercharger looks due in APRIL or MAY
Turbo kit they are hoping on March or April.

This is all I have right now, this is busy season...

 

So much for those dates....

Any updates?

 

i saw in turbo magazine an add for blitz. it had a pic of an rx-8 and said rx-8 compressor coming soon...but who knows when that could be.

 

Try search? :p

Look at the BLitz supercharger threads... and yes it's a s/c NOT a t/c.

 

I wonder how Phoenix's Power is doing with their turbocharged RX-8? I remember it using a T67, but they didn't have any final specs.

 

Oh yea what about .6 second cars:D .