SC and TT Characteristics Compared & Discussed

[nota4re]

On another thread regarding a TT install, our friend Eric (AtomicGT) said,

Congratulations, Impressive. Any estimate on the engine life with that kind of BHP?

That got me thinking of a way to try to compare and discuss the differences of the SC set-up to a TT set-up. The root of the question assumes that RWHP is an indication of how much overall "work" the engine is actually performing. Conceptually, it would seem that an engine with 600 RWHP has a lot less strain on it compared to an engine with 800 RWHP. This is really NOT the case if the method of forced induction is not the same.

I looked through some files I had here on the laptop and tried to find some dyno charts that would illustrate this point. In particular, I tried to find an SC chart and a TT chart where the boost pressures were as similar as possiple. I *almost* succeeded in the following:



It would have been great if the boost pressures were identical, but with max difference of about 1PSI, I think we can consider them close enough to illustrate some of our points. (I left the TQ curve off just to simplify the graphs.) The first thing to notice is that the SC is really superior to bring on boost much earlier than the TT is capable of. The HP graph shows this well with the SC "ruling the roost" below 4,000 RPM. At approx 4200 RPM the TT has finally matched the boost levels of the SC and sure enough, this is where the HP ouput is also the same.

But the real differences between the SC and the TT can be seen in what happens North of 4200 RPM. If you look at the the boost graph, the boost levels are approximately the same and flat from 4200 RPM up. To maintain constant boost pressures, the TT set-up is bleeding off EXHAUST (not boost) pressure via the wastegates. The Supercharger starts falling out of an efficiency curve and the engine is expending a lot of power to turn the supercharger - power that is not being measured by the dyno at the rear wheels. And the net result... more than 200 RWHP provided to the rear wheels via the TT.

Let's get back to AtomicGT's original question. So, in this simple (admittedly inexact) example, which engine is working harder and could ultimately incur a shorter lifespan. In my view, the two engines in this example are doing approximately the same work. The TT is doing a better job of getting more power to the ground at the top end, while the SC has a clear advantage at the low end.... but is exerting a tax at the upper RPM range.

 

[BlackICE]

Kendall well said!

Now depending on how you drive your car you can see what system fits your style better. Stay most of the time below 4.5K the blower will give you a better fit. Love the rush as you pull to and past 6K the TT is the way to go. Plan to do over 200 in the standing mile TT!

One can augment the torque and HP where the blower falls off by installing a NOS system. Then you can have the low end of a blower with the high end of a TT!

I think Soroush has proven that! :biggrin

Of course people will be saying you are on the "bottle."

 

[2112]

The TT sure would benefit with the shorter Ring gear ratio. Just stating the obvious. :biggrin
.

 

[avjunky]

Nice Comparison! It would be interesting to compare the torque figures as well. Do you have those?

 

[Luke Warmwater]

It would be interesting to see a Whipple in this comparison as well.

 

[nota4re]

It would be interesting to see a Whipple in this comparison as well.

Agreed. Anybody have any .drf dyno files they can email me? The hard part is trying to find charts with the same amount of boost - so that at lease there is some locking point between the two graphs. In the chart above, I'm not sure that anyone who went through the time and expense for a TT would run "just" 16lbs of boost. More likely you will find owners at 18-20psi and another 100HP or so at the wheels above what we see here.

Another anomaly of the chart above is that it doesn't clearly enough show the benefit of the SC in the lower RPM range. With dyno "start" on the SC pulley/tune set-up really didn't get started until a higher RPM, but clearly you can extend the line over and see the advantage at the lower R's. In contrast, the TT run was a "set-up" run and we tried to load the car early (2K RPM) to see the broadest graph as possible. Anyway, neither of these nuances effect the "gross" conclusions of the work being placed on the engine.

To the point the Shadowman made in a different post, when you look at the graphs you begin to see how the cars will have such a different feeling when driven. There may be no one is better than the other, but owners may decide on their own HP delivery preferences.

 

[Shadowman]

Agreed. Anybody have any .drf dyno files they can email me? The hard part is trying to find charts with the same amount of boost - so that at lease there is some locking point between the two graphs. In the chart above, I'm not sure that anyone who went through the time and expense for a TT would run "just" 16lbs of boost. More likely you will find owners at 18-20psi and another 100HP or so at the wheels above what we see here.

Another anomaly of the chart above is that it doesn't clearly enough show the benefit of the SC in the lower RPM range. With dyno "start" on the SC pulley/tune set-up really didn't get started until a higher RPM, but clearly you can extend the line over and see the advantage at the lower R's. In contrast, the TT run was a "set-up" run and we tried to load the car early (2K RPM) to see the broadest graph as possible. Anyway, neither of these nuances effect the "gross" conclusions of the work being placed on the engine.

To the point the Shadowman made in a different post, when you look at the graphs you begin to see how the cars will have such a different feeling when driven. There may be no one is better than the other, but owners may decide on their own HP delivery preferences.

The reason that the TT looks closer to the supercharged gal on a dyno chart is because on the dyno the turbos are “already” spooled” up whereas if being driven on the street this is “not” the case as such the notorious turbo lag is pronounced on the street until they reach approximately 4000 rpm. The spooling of the turbos requires load whereas the supercharger simply needs the engine to spin. Now you can manage this on the street by power braking etcetera for example before leaving from a stop light in the same way pro drag racers do however it makes for a less than fluid driving style.

You cannot have an apples to apples comparison on a Dyno Jet or Mustang dyno so the overlaying of the charts would be interesting at best.

Takes care

Shadowman

 

[nota4re]

The reason that the TT looks closer to the supercharged gal on a dyno chart is because on the dyno the turbos are “already” spooled” up whereas if being driven on the street this is “not” the case as such the notorious turbo lag is pronounced on the street until they reach approximately 4000 rpm.

Clearly, the charts show the spooling up of the turbos as you can see the boost pressure climbing until approx. 4,000 RPM where they finally match the boost pressure tha the SC has been providing all along. If the turbos were "already spooled" as you contend, we would have near instantaneous boost pressures where we clearly do not. Instead, we see a dyno chart that depicts pretty closely how the car feels and drives on the street. What the chart omits - and I said it in a prior post is tha the SC's lower RPM reach is even further - it simply wasn't captured in the dyno run example.

Its a little disconcerting to see a trend of one person trying to refute every post of another member. Perhaps there's better ways to spend ones time.

 

[Shadowman]

Clearly, the charts show the spooling up of the turbos as you can see the boost pressure climbing until approx. 4,000 RPM where they finally match the boost pressure tha the SC has been providing all along. If the turbos were "already spooled" as you contend, we would have near instantaneous boost pressures where we clearly do not. Instead, we see a dyno chart that depicts pretty closely how the car feels and drives on the street. What the chart omits - and I said it in a prior post is tha the SC's lower RPM reach is even further - it simply wasn't captured in the dyno run example.

Its a little disconcerting to see a trend of one person trying to refute every post of another member. Perhaps there's better ways to spend ones time.

BTW noat4re; huum do I read a hint of sarcasm? as I truly desire not to frustrate you and your sharing of information.

Now before I proceed let me be clear; I am a performance and motor knutt and enjoy both supercharged and turbo applications; I like pressured systems however.

I see that at roughly 4250 RPM is when the supercharged gal and the turbo gal have the same boost; initially I read the chart incorrectly as I though I was looking at a HP and Torque curve; so sorry. Nonetheless it shows that as I have shared with "all" that ask that at approximately 4200 RPM in a turbo gal based on the system design as presented that they will feel as though shot out of a cannon however up until that point it is a waiting game and this is when compared to the gal with the supercharger that has remained frisky the entire time.

After tending to these gals for over 30 years I do have the flavor I like most for “street” applications and at the same time am very aware of the differences between them.

You graph is truly spot on; it shows that 2000 RPM there is little or “no” boost and even as high as 3800 RPM there is barely 10 PSI of boost as such what I refer to as a lazy peddle when compared to a supercharged gal the boost would have pegged at 2000-2200 and maintained a flat line across the operating range of most people specifically 2- 6000 RPM and then a supercharged gal will fall off slightly as the load decreases whereas the turbo gal will typically remain flat beyond that point. These engines by design are low compression as such lacking boost down low changes the driving characteristics of the gals as if comparing day to night.

Now please do not misread that which I am about to say;

If I/most folks step on the go pedal and at 2000 RPM already have maximum boost available to them this because of the operational characteristics of a supercharger whereas with a turbo gal I/folks have to wait until over 4000RPM for the same boost which will give you the gross stump pulling torque and pleasure as associated with it during a typical on the street driving; for me it is the supercharger, this is based on the turbo system that you are sharing the operation data for.

In my world I want all the power “now” however you seem to think that the resulting numbers beining similar will create a similar driving experience; sadly this is not the case.

Is one better than another; “NO” but discernibly different

Now as for my time; I wil continue to allocate that which seems needed and enjoy the process as associated with it.

Takes care and your comments are appreciated even though they did seem a bit personal; I share much on this forum and it is not because I expect one to adopt my ways but rather so they have another opinion.

Shadowman

 

[nota4re]

OK, Bill, I try to make this as non-personal and as politically correct as possible. I think we have *MUCH* more in common than not in common - and certainly we share a passion for cars... and once again we may both be addicts of forced induction!

My sarcastic/personal comments were intended to get your attention as has happened in the past, I think you have seen so much and have so much knowledge (NO SARCASM HERE) that you get ahead of yourself.

Please try to analyze the graphs I provided because you are making assumptions and coming to conclusions BEFORE you have understood what is presented. As such, you are remarking about things completely out of context.

Now another thing; FYI your dyno chart is skewed because HP and Torque have a 5250 crossing point whereas your chart shows this happening at roughly 4250; how can this be?

The chart does NOT show any TQ curves at all. This is two HP curves - one of a pulley'd OEM SC, and the other of a (almost equally boosted) TT set-up.

You graph is truly spot on; it shows that 2000 RPM there is little or “no” boost and even as high as 3800 RPM there is barely 10 PSI of boost

Exactly. But previously you said that,

The reason that the TT looks closer to the supercharged gal on a dyno chart is because on the dyno the turbos are “already” spooled” up whereas if being driven on the street this is “not” the case as such the notorious turbo lag is pronounced on the street until they reach approximately 4000 rpm.

So, sometimes I think you are in an argumentative/cantankerous mood! :biggrin

This is why you earned the "completely wrong" remark.... because your assessment really was in error, while your knowledge/background, clearly is not. Further, you go on to say,

In my world I want all the power “now” however you seem to think that the resulting numbers beining similar will create a similar driving experience; sadly this is not the case.

So, now you are saying that I think the driving experience will be the same???? (I just hate it when people tell me what I think - especially when they are wrong :eek) I'm sorry, my friend, but I am saying exactly the opposite. I'm not only saying the driving experience will be very different, I have attempted to show/quantify why that is the case.

And in summary you will find that we are largely in agreement - the only question is why we have to endure the attacks in order to get here.

I have much more to write/observe about the SC/TT comparisons, so I hope we can move forward!!

 

[Shadowman]

OK, Bill, I try to make this as non-personal and as politically correct as possible. I think we have *MUCH* more in common than not in common - and certainly we share a passion for cars... and once again we may both be addicts of forced induction!

My sarcastic/personal comments were intended to get your attention as has happened in the past, I think you have seen so much and have so much knowledge (NO SARCASM HERE) that you get ahead of yourself.

Please try to analyze the graphs I provided because you are making assumptions and coming to conclusions BEFORE you have understood what is presented. As such, you are remarking about things completely out of context.



The chart does NOT show any TQ curves at all. This is two HP curves - one of a pulley'd OEM SC, and the other of a (almost equally boosted) TT set-up.



Exactly. But previously you said that,



So, sometimes I think you are in an argumentative/cantankerous mood! :biggrin

This is why you earned the "completely wrong" remark.... because your assessment really was in error, while your knowledge/background, clearly is not. Further, you go on to say,



So, now you are saying that I think the driving experience will be the same???? (I just hate it when people tell me what I think - especially when they are wrong :eek) I'm sorry, my friend, but I am saying exactly the opposite. I'm not only saying the driving experience will be very different, I have attempted to show/quantify why that is the case.

And in summary you will find that we are largely in agreement - the only question is why we have to endure the attacks in order to get here.

I have much more to write/observe about the SC/TT comparisons, so I hope we can move forward!!

nota4re stated the following about Shadowman "sometimes I think you are in an argumentative/cantankerous mood! :biggrin"

Sometimes this is the case however it takes a bur getting stick under my shirt to initiate it; LOL There is no doubt that at times I am a fricken PITA to you however let me be clear that there are times that these feelings are mutually shared and yet I take none of it personally.

nota4re I "like" all the personal touches that folks do to make the gals their own even those that have a pair of hair dryers however ......... folks need to know the differences and sharing like HP numbers and even how the torque is the same at some moment in time is IMO misleading; most folks do not know what the dyno chart is sharing but rather have learned to discuss one thing; “horsepower” as if this is the Holy Grail.

So as they say "can we all get along" absolutely as we have for years sharing personal experiences, differing viewpoints, and at times unfounded opinions.

nota4re I have no agenda defined and yet if asked why I spend as much time as I do on the forum and chatting with folks about their gals it is simply because I care. I like it when as informed folks they make decisions and find the results consistent with that which they expected.

I did edit my post after commenting on the 4250 RPM cross over point because frankly I went back and looked at the graph again because even as I was typing the comment it made no sense to me; I did apologies for this and wanted to and did clear this immediately.

Now with regards to the spooling of the turbos and how they can be loaded hence spooled up in advanced of the dyno pull, my comments remains because I read that you were comparing the fact that the two system could in fact create similar operational characteristics; this is not true.

So where are the torque curves; IMO these mean more than the HP because this is a real number and the act of creating it is what folks feel and to the greatest degree enjoy? A 1000 HP gal with no power aka torque developed down low would be miserable to drive and yet could be very fast on the big end.

Please share the torque curves as the basis to move forward; I for one am ready.

Takes care

Shadowman

 

[STORMCAT]

opopopop

 

[nota4re]

First.... oh, shuttup Brian... go work on those Ceramic Brake Kits..... Bill and I is trying to have a conversation here. :biggrin

Bill, I'm gonna add now the word "stubborn" because you don't want to take a man at his word. Namely,

Now with regards to the spooling of the turbos and how they can be loaded hence spooled up in advanced of the dyno pull, my comments remains because I read that you were comparing the fact that the two system could in fact create similar operational characteristics; this is not true.

First point.... where the heck did I say they could have similar operational characteristics? I said, have said, and keep saying that the SC's "rule the roost" below 4K. Does that sound to you like I am saying there is similar operational characteristics??? (Do you read what I write or assume to know what I'm thinking??)

Second point.... if you look at the charts, do you really believe that the turbos were spooled up in this test? C'mon now, be serious. In just your previous post you said,

You graph is truly spot on; it shows that 2000 RPM there is little or “no” boost and even as high as 3800 RPM there is barely 10 PSI of boost

I'm SOOOOO CONFUSED!

OK, TQ charts coming when I get home.... and we try to move forward. Back to our regular programming.

 

[Mullet]

I say the SC\TT setup is a better all around setup because of no lag at any rpm.

Also I believe it's a better setup for a stock motor running Mile events. I know of a few TT setups that have run mile events and they are getting in the low 220's when my setup got a few more mph's. I'm just sayin'.

 

[tmcphail]

I'm just sayin'.

And that is precisely all your doing.

 

[Mullet]

And that is precisely all your doing.

????

 

[tmcphail]

Oh and from my perspective with a car set up blower / blower NOS / TT / TTSC then back to TT. For me personally I love the turbos alone above any other setup.

But that again is personal preference. Anyone doing research needs to spend time in a vehicle that they may have interest in too see what fits within their realm of happiness.

 

[Black GT]

I say the SC\TT setup is a better all around setup because of no lag at any rpm.

Also I believe it's a better setup for a stock motor running Mile events. I know of a few TT setups that have run mile events and they are getting in the low 220's when my setup got a few more mph's. I'm just sayin'.

You have a Hennessy set up right? Stock blower with twins? How do you like her?

 

[skyrex]

All the technical stuff is a bit beyond me. All I do know is what they feel like to drive.

I can give first impressions of driving my TT after having put 300 miles in over the weekend. Obviously my SC is still fresh in my mind. That said they are two totally different feels when driving. Everything from how the car reacts during acceleration, downshifts to slow down a bit in traffic, is different. SC acceleration gives you a bit more at the bottom end (meaning 1st gear......but I if I remember correct first gear in my TT set-up is limited to prevent some wheelspin) however acceleration from there is totally different. The SC puts you back in your seat but the acceleration while fast is steady and after fourth takes its time to the high mph's.....you know what number I mean. :lol The TT acceleration, as long as your tires can hold, is aggressive through every gear till you decide to lift off the pedal. Put it this way, I have less wrinkles today then yesterday. I do not regret the little bit I lost on the low end at all. :cheers

Just an opinion of a guy with a fresh TT smile who has limited understanding of the tech arguments of earlier posts. :cheers

 

[Shadowman]

First.... oh, shuttup Brian... go work on those Ceramic Brake Kits..... Bill and I is trying to have a conversation here. :biggrin

Bill, I'm gonna add now the word "stubborn" because you don't want to take a man at his word. Namely,



First point.... where the heck did I say they could have similar operational characteristics? I said, have said, and keep saying that the SC's "rule the roost" below 4K. Does that sound to you like I am saying there is similar operational characteristics??? (Do you read what I write or assume to know what I'm thinking??)

Second point.... if you look at the charts, do you really believe that the turbos were spooled up in this test? C'mon now, be serious. In just your previous post you said,



I'm SOOOOO CONFUSED!

OK, TQ charts coming when I get home.... and we try to move forward. Back to our regular programming.

It is all good

Shadowman