So How much Lag is there with these Systems

[snowmotion]

I here people talk of Turbo Lag time I Get Lag with mine Without a Turbo
I Want to find the Snappiest Nasty Rip my Arms off Scare the snot out of me responce to get my Leggs Draggin in the wind behind me like a cartoon or a Bill Cosby Sheby Cobra. really I want Responce I can Get out of a hole In a Flick of A thumb I dont Know If I am as worried about Lag as Bogging out I just like to Know When I hit the Trigger #*$&@ Happens
I have seen lots of stock & Mod sleds bog which is more iratating than lag
getting that INSTANT Go Power is the Feel I Crave

 

[LazyBastard]

Bog is usually due to carburation. If you're running at high altitude, its probably very rich at the low end. Try lowering your needles.

 

[black john]

turbo

unles you lower the comp in order to run more psi it should be the same as stk untill the turbo gets to boost psi witch should happen fairly fast if its clutched right. frouy mount turbos should be a little faster to come on than rear as there is less pipeing. but the trend is going to rear mounted on most systems. hope this helps. john

 

[ken_climb]

Front mounted turbo's have very little or no lag at all. Rear mounts in general have more lag,but it can definitely be helped by clutching .When I first got mine installed we tried some weights in the clutch that were obviously to light cause I would punch it and it would rev instantly to 11,000rpm and bounce off the rev limiter with virtualy 0 lag.Then we put in some heavier weights and it felt like it increased the lag to maybe a split second ,but then hold the f..k on like you never have before!
No bogging or anything like you're describing though.

 

[lakercr]

Oh boy, another post on turbo lag!!

OK, just kidding...

Here is my perspective on the topic.

Start with a definition of these three terms; boost threshold, lag, and throttle response.

Boost Threshold - lowest engine RPM that will produce an intake pressure above atmospheric in the intake.

Lag - The delay between a change in throttle position and the arrival of noticeable boost (assuming that you've given the engine enough throttle to build boost - see boost threshold).

Throttle Response - A change in engine RPM resulting from a change in throttle position.

Boost Threshold is primarily a function of turbo sizing. A smaller turbo will (all other things being equal) spool faster, creating boost at a lower engine RPM. The trade off to this is that if the turbo is too small for the application it will be lacking on power in the higher RPM range (bad), operating outside of the efficiency curve for the turbo (more bad) and you will create excessive amounts of exhaust gas back pressure (extra bad). Alternatively, a turbo that is too large for the application may be well into the operating range of the engine before it mades any boost at all, which in most cases would not be a design goal of the fabricator. A properly sized turbo for a particular application will include having a low boost threshold as (one) of it's design parameters.

Assuming that you haven't reduced the compression ratio of the engine substantially, and that the intake plumbing does not introduce any unneccessary restriction to the system, the engine's torque curve up to the boost threshold will remain the same as it always was. When you hit the boost threshold, a rider will feel an "extra" surge in acceleration as the engine's torque curve takes a leap upwards. As an example, if a turbo RX has a boost threshold of 6K, there would be a short elapse of time between applying the throttle and feeling that surge of power, 5K threshold - less so, and so on.

The question was asked regarding Lag and throttle response. Really, the two are independant. Your throttle response will remain the same with or without the turbo, you'll just have a lot more torque to play with after a certain RPM. If your clutching and jetting are right on the RX for the conditions you ride in, you should have very crisp throttle response on the bottom end. The comment above that "I have lag even without the turbo" is very true. If by definition lag is the time elapse between the application of throttle and the arrival of boost pressure, then yes, your lag is infinite without a turbo.

What I think is really being asked in this (and other posts) is how long is the wait for that kick in the #*$&@ when I pinch the throttle? That discussion usually goes straight to a debate on the merits of various locations for mounting the turbo in a system. I believe that there are more significant issues to address (as mentioned above) than singling out that one element of design ctiteria. That said, before you can build boost, you must pressurize the intake. Therefore, a system with more plumbing, an intercooler, etc. will take longer to fill than one with less (or none). With respect to the current offerings on the market then, a turbo with virtually no intake plumbing (or intercooler), should make boost quicker than a "front" mounted turbo, which should in turn build quicker than a "rear" mounted turbo - all things being equal. Of course, things are not all equal, and there are many other important things to consider when choosing a kit. Consider also that the air coming out of the compressor is travelling a little over 300MPH - the time it takes to pressurize the intake of any system is only a fraction of a second. As well, lag decreases as RPM increases - for the vast majority of your time on the sled response should feel instantaneous with any of the kits.

Hope that helps to answer your question, I really don't want to get into a big debate over this kit vs. that kit. There are many important factors to consider when choosing a kit, this is only one of them. I'll offer that I was at Haydays last week-end and had a chance to see both the CPR and Bender products up close (sorry Jason, didn't find Tom). They are both VERY well done kits, and set the bar high for others wanting to compete in this space.

 

[spray25]

That is bar none the best, most thurough explanation to date.

Good post. Wait, no, GREAT post!!!

Also remember clutching has a DRAMATIC effect on the perceived "lag".

 

[jtssrx]

lakercr: Jim I talked to Curt and he told me he would do some coatings for you to test with. He said he has been coating some local guys turbos for car applications and they are getting quicker spool up times with the coated housings. These times are recorded so they 100 percent accurite.

 

[lakercr]

Great - thanks Jason, I'll give you a call to discuss details.

 

[snowmotion]

I guess GOOD Tuning And Clutching is the real issue

Thanks I guess the facts are that GOOD Tuning And Clutching is the real issue with all systems I guess I will need to spend a little more time at that rather than Just Piling on the Miles as I do now
For you out east It is COLD here NOW and we are starting to get snowfalls
The snows are not staying Long but I am starting to Plan on a DEEP STEEP LONG Winter around here.
I just gotta Get My Boost for this season Organized

 

[Silverbullet]

Lakercr, Excellent article It's always great to see the effort some people put into this site

 

[lakercr]

Just wait for my piece on why black sleds are fastest....

 

[spray25]

Just wait for my piece on why black sleds are fastest....

And here I thought you were a credible source

 

[lakercr]

Sorry Spray, what I meant to say was that black is fastest, but the blue ones climb the best - Better?

 

[spray25]

Much better.

 

[turbo1320]

Oh boy, another post on turbo lag!!

OK, just kidding...

Here is my perspective on the topic.

Start with a definition of these three terms; boost threshold, lag, and throttle response.

Boost Threshold - lowest engine RPM that will produce an intake pressure above atmospheric in the intake.

Lag - The delay between a change in throttle position and the arrival of noticeable boost (assuming that you've given the engine enough throttle to build boost - see boost threshold).

Throttle Response - A change in engine RPM resulting from a change in throttle position.

Boost Threshold is primarily a function of turbo sizing. A smaller turbo will (all other things being equal) spool faster, creating boost at a lower engine RPM. The trade off to this is that if the turbo is too small for the application it will be lacking on power in the higher RPM range (bad), operating outside of the efficiency curve for the turbo (more bad) and you will create excessive amounts of exhaust gas back pressure (extra bad). Alternatively, a turbo that is too large for the application may be well into the operating range of the engine before it mades any boost at all, which in most cases would not be a design goal of the fabricator. A properly sized turbo for a particular application will include having a low boost threshold as (one) of it's design parameters.

Assuming that you haven't reduced the compression ratio of the engine substantially, and that the intake plumbing does not introduce any unneccessary restriction to the system, the engine's torque curve up to the boost threshold will remain the same as it always was. When you hit the boost threshold, a rider will feel an "extra" surge in acceleration as the engine's torque curve takes a leap upwards. As an example, if a turbo RX has a boost threshold of 6K, there would be a short elapse of time between applying the throttle and feeling that surge of power, 5K threshold - less so, and so on.

The question was asked regarding Lag and throttle response. Really, the two are independant. Your throttle response will remain the same with or without the turbo, you'll just have a lot more torque to play with after a certain RPM. If your clutching and jetting are right on the RX for the conditions you ride in, you should have very crisp throttle response on the bottom end. The comment above that "I have lag even without the turbo" is very true. If by definition lag is the time elapse between the application of throttle and the arrival of boost pressure, then yes, your lag is infinite without a turbo.

What I think is really being asked in this (and other posts) is how long is the wait for that kick in the #*$&@ when I pinch the throttle? That discussion usually goes straight to a debate on the merits of various locations for mounting the turbo in a system. I believe that there are more significant issues to address (as mentioned above) than singling out that one element of design ctiteria. That said, before you can build boost, you must pressurize the intake. Therefore, a system with more plumbing, an intercooler, etc. will take longer to fill than one with less (or none). With respect to the current offerings on the market then, a turbo with virtually no intake plumbing (or intercooler), should make boost quicker than a "front" mounted turbo, which should in turn build quicker than a "rear" mounted turbo - all things being equal. Of course, things are not all equal, and there are many other important things to consider when choosing a kit. Consider also that the air coming out of the compressor is travelling a little over 300MPH - the time it takes to pressurize the intake of any system is only a fraction of a second. As well, lag decreases as RPM increases - for the vast majority of your time on the sled response should feel instantaneous with any of the kits.

Hope that helps to answer your question, I really don't want to get into a big debate over this kit vs. that kit. There are many important factors to consider when choosing a kit, this is only one of them. I'll offer that I was at Haydays last week-end and had a chance to see both the CPR and Bender products up close (sorry Jason, didn't find Tom). They are both VERY well done kits, and set the bar high for others wanting to compete in this space.

Good info