Need some help...not happy with Dyno results

[Alloy Dave]

Originally Posted by Birdman

Correction...that is that torque cruve which is normal for these cars.

no George, I was talking about the HP curve. Maybe I should not have used the word "flat"...but I'm used to seeing the HP curve have a bit of a "rounded" look to it ...in other words it tapers off as it gets up over 4500 or so...but this one looks different. Maybe it's my imagination.

Dave

[Birdman]

Originally Posted by Alloy Dave

no George, I was talking about the HP curve. Maybe I should not have used the word "flat"...but I'm used to seeing the HP curve have a bit of a "rounded" look to it ...in other words it tapers off as it gets up over 4500 or so...but this one looks different. Maybe it's my imagination.

Dave

(RED LINE=power)
Dave,It has a straight climb upwards (no taper) untill 5800 rpm then it falters a bit until the 6050 mark then climbs a bit more until the 6250 mark. Not sure where you see it flat except at the 5800 mark.


http://www.stangmafia.com/forum/atta..._hodgson_1.pdf

[68fastback]

Dave, if I'm reading you right you're saying that the HP line is very 'straight' (nearly constant slope) rather than asymptotically curving as it approaches the peak power level -- the more traditional HP curve.

Check the boost curve -- I think that's the key. It starts out building slow, stays rather flat/constant in mid range, but then starts turning up again (and with increasing slope) at the top ...right where you'd expect HP to start leveling ...and that's why HP doesn't ...it remains 'straight' upward.

Dunno if that's a characteristic of the 2.9s long-slim rotors or what ...not necessarily a bad thing at all, but very tempting to push the revs too high when it's pulling like a freight train at redline. Kinda says this SC wants more pulley so the SC rpm are pulled in realtive to engine RPM. Of course that means a lot more potential power ...which may or may not be a realistic goal on 93 octane.

Curious what pulley is on it and if that characteristic boost curve changes with a smaller pulley or if it just shifts left (relative to engine rpm) with more rotor speed.

Dunno, but I'd guess, by comparo, the TVS is more linear just because it's a simple roots pump ...also not necessarily a bad thing, just a different SC 'signature.' Any one have a boost curve handy on a nice free breathing intake/exhaust with a TVS?

Now you've gotten me curious.

[Vette Killer]

Originally Posted by 68fastback

Dave, if I'm reading you right you're saying that the HP line is very 'straight' (nearly constant slope) rather than asymptotically curving as it approaches the peak power level -- the more traditional HP curve.

Check the boost curve -- I think that's the key. It starts out building slow, stays rather flat/constant in mid range, but then starts turning up again (and with increasing slope) at the top ...right where you'd expect HP to start leveling ...and that's why HP doesn't ...it remains 'straight' upward.

Dunno if that's a characteristic of the 2.9s long-slim rotors or what ...not necessarily a bad thing at all, but very tempting to push the revs too high when it's pulling like a freight train at redline. Kinda says this SC wants more pulley so the SC rpm are pulled in realtive to engine RPM. Of course that means a lot more potential power ...which may or may not be a realistic goal on 93 octane.

Curious what pulley is on it and if that characteristic boost curve changes with a smaller pulley or if it just shifts left (relative to engine rpm) with more rotor speed.

Dunno, but I'd guess, by comparo, the TVS is more linear just because it's a simple roots pump ...also not necessarily a bad thing, just a different SC 'signature.' Any one have a boost curve handy on a nice free breathing intake/exhaust with a TVS?

Now you've gotten me curious.

Right now it has a 3.25" pulley and a standard lower, also going to try a 3.00" as the sweet spot for efficiency on a 2.9 is supposed to be 15 PSI and above (keep in mind the boost readings on the graph are 2 PSI low)...and potentially could be about 15 HP per PSI increase; the 3.00" should be good for another 3.5 to 4 PSI at least

Going over the rest of the data there is still a lot of fuel left, an updated cooler will be another step along the way as well.

After some discussion with the tuner and a couple of other people who are chasing improvements with him I am a lot less concerned about the results....I will try and get some other results as well as one has a TVS and GT cams and the other is a KB 2.8 with a twin 75 mm TB; we all have similar exhaust setups but different rear ends; the TVS car has a 4.10 and the KB is still a 3.31

Just for the hell of it I am going to find someone with a Dynojet so I can get a comparison

[Alloy Dave]

Originally Posted by Birdman

(RED LINE=power)
Dave,It has a straight climb upwards (no taper) untill 5800 rpm then it falters a bit until the 6050 mark then climbs a bit more until the 6250 mark. Not sure where you see it flat except at the 5800 mark.


http://www.stangmafia.com/forum/atta..._hodgson_1.pdf

See Dan's post....he understands what I'm saying.

Originally Posted by 68fastback

Dave, if I'm reading you right you're saying that the HP line is very 'straight' (nearly constant slope) rather than asymptotically curving as it approaches the peak power level -- the more traditional HP curve.

Check the boost curve -- I think that's the key. It starts out building slow, stays rather flat/constant in mid range, but then starts turning up again (and with increasing slope) at the top ...right where you'd expect HP to start leveling ...and that's why HP doesn't ...it remains 'straight' upward.

Dunno if that's a characteristic of the 2.9s long-slim rotors or what ...not necessarily a bad thing at all, but very tempting to push the revs too high when it's pulling like a freight train at redline. Kinda says this SC wants more pulley so the SC rpm are pulled in realtive to engine RPM. Of course that means a lot more potential power ...which may or may not be a realistic goal on 93 octane.

Curious what pulley is on it and if that characteristic boost curve changes with a smaller pulley or if it just shifts left (relative to engine rpm) with more rotor speed.

Dunno, but I'd guess, by comparo, the TVS is more linear just because it's a simple roots pump ...also not necessarily a bad thing, just a different SC 'signature.' Any one have a boost curve handy on a nice free breathing intake/exhaust with a TVS?

Now you've gotten me curious.

I went to the dyno chart thread and picked 3 at random. At about 5300 on these three, you start to see it tailing off...but I don't see that in his post above.

http://www.stangmafia.com/forum/128266-post1.html - Dave

http://www.stangmafia.com/forum/403-post1.html - iceman

http://www.stangmafia.com/forum/25181-post1.html - gr8snkbites

All three of these have much more of a curved appearance than his...just seems a bit odd.

[Birdman]

Originally Posted by Alloy Dave

See Dan's post....he understands what I'm saying.



I went to the dyno chart thread and picked 3 at random. At about 5300 on these three, you start to see it tailing off...but I don't see that in his post above.

http://www.stangmafia.com/forum/128266-post1.html - Dave

http://www.stangmafia.com/forum/403-post1.html - iceman

http://www.stangmafia.com/forum/25181-post1.html - gr8snkbites

All three of these have much more of a curved appearance than his...just seems a bit odd.

I understand what you mean now Dave I was just thrown off you saying it looked "flat" as in leveling off.
I agree there is something a bit unusual near the top of the graph about both the power curve and the torque curve in that graph especially the torque curve.

[ShelbySteve]

If you could dyno it on a Dynojet I could possibly make some comparisons but the Mustang Dyno is a whole different thing. Some read high, some read low. I think it depends on how and who sets it up. I can change my Dynojet readings slightly but only a bit. Not enough to make a big difference.

The Whipple 2.9 is an odd egg as they say. I think it has the potential to be a strong s/c but when they said tuner kit, they.... "Whipple".... wasn't kidding.

I posted over on T/S that all the 2.9 dyno's I have seen had to exceed the 6250 redline to make the power that would be expected. As it stands and I have driven my 2.9 and put about 100 miles on it. My modded Tvs was faster/more responsive up to around 5k rpm. I have the 2.9 running pretty close to the Tvs now but it still comes up a little short.....on the street.

After 5k up to 6800 if you want to turn it that high the Whipple beats my Tvs......But who the hell wants to turn a stock GT500 engine that high to make the HP.

I have the 3" upper and the 10% lower on it currently. I personally think it needs to spin a little faster so we can see the peak power levels at 6k to 6300. But what kind of boost and what kind of fuel will we have to run? I also noticed that the few 2.9's other than mine that I know of run 20 degrees timing for the street tune to get the HP up. It also seems like the 2.9 likes timing.

I am still experimenting when time permits and hope to have more soon. I also just hope this isn't the Edsel of superchargers.....quality product but just doesn't quite make it.

Good luck with your 2.9 I look forward to more updates.

[Vette Killer]

Originally Posted by ShelbySteve

If you could dyno it on a Dynojet I could possibly make some comparisons but the Mustang Dyno is a whole different thing. Some read high, some read low. I think it depends on how and who sets it up. I can change my Dynojet readings slightly but only a bit. Not enough to make a big difference.

The Whipple 2.9 is an odd egg as they say. I think it has the potential to be a strong s/c but when they said tuner kit, they.... "Whipple".... wasn't kidding.

I posted over on T/S that all the 2.9 dyno's I have seen had to exceed the 6250 redline to make the power that would be expected. As it stands and I have driven my 2.9 and put about 100 miles on it. My modded Tvs was faster/more responsive up to around 5k rpm. I have the 2.9 running pretty close to the Tvs now but it still comes up a little short.....on the street.

After 5k up to 6800 if you want to turn it that high the Whipple beats my Tvs......But who the hell wants to turn a stock GT500 engine that high to make the HP.

I have the 3" upper and the 10% lower on it currently. I personally think it needs to spin a little faster so we can see the peak power levels at 6k to 6300. But what kind of boost and what kind of fuel will we have to run? I also noticed that the few 2.9's other than mine that I know of run 20 degrees timing for the street tune to get the HP up. It also seems like the 2.9 likes timing.

I am still experimenting when time permits and hope to have more soon. I also just hope this isn't the Edsel of superchargers.....quality product but just doesn't quite make it.

Good luck with your 2.9 I look forward to more updates.

Thanks for sharing your experience too....I am thinking there will be more potential in these as they get out there and more people work on tunes as well. Your comments are very similar to the discussion I had with my tuner on what can we do to lower the peak power curve....who knows, if it wants to keep living up in that high RPM range even after spinning the blower faster it may be time to update the rods, put in an updated cam drive arrangement that will live at high RPM and let 'er rip....those heads with a little massaging and the GT cams should be good for 7500 - 8000 all day long long

[ShelbySteve]

Yep, I am working on putting together another engine so I am not limited by the rods. That may be the thing to do in the long run. I just need my current engine to last until next spring..........damn this is an expensive hobby!

[68fastback]

VetteKiller's curves and what ShelbySteve is observing seem consistent with what I was suggesting and what the dynos Dave posted are supporting (thanks for posting those, Dave ...I didn't think to look in the dyno thread ).

With a smaller pulley the 2.9 boost curve should pull-in (relative to engine rpm) and shape-wise might look much like icemen's KB boost curve and, therefore, a HP curve that peaks within the usefull rpm range for a street engine ...at least that's what I'm thinking (and what caught Dave's eye on the 2.9).

As expected, the TVS boost curve (gr8snkbite's dyno) is very linear (simple efficient pump) so peak-Tq relative to peak-HP will be higher than with a twinscrew's non-linear (flat reverse-S) curve -- and ShelbySteve's observations seem to bear this out. This makes sense too just because the average value of an S-curve relative to its peak will always have more variation than the average of a linear curve (line) relative to its peak -- since a flat line (slope=0) exhibits peak and average at any point by definition).

With twinscrews (which just happen to be substantially larger and therefore capable of more peak boost for any given engine displacement) the peak-Tq relative to peak-HP should be lower than a roots due to that 'build-flat-build' (reverse S-curve) shape of the twinscrew boost curve -- assuming it's a universal twinscrew signature ...dunno, but suspect so. (possibly it has to do with case-compression overhead unique to twinscrews ...dunno, just a swag).

Other things being equal, I'm thinking VetteKiller's HP curve will flatten at peak (Dave's question) if the peak boost is pulleyed-in such that it start to flatten before peak engine rpm.

If the peak is pulled-in, you may then be overspinning the SC bearings at the top end (which the twinscrew manufacturers all say is no problem, but I'm not sure I believe that longterm unless the bearing mfgrs change their spec). Just the fact that twinscrews rotors must spin at different rpm creates this potential problem.

To my mind the higher *relative* Tq of the linear pump has street advantages tho the big non-linear response of the larger twinscrews are capable of big peak HP. You say po-ta-to, I say po-tah-to -lol. Two different SC 'signatures' ...at least that's what I think we're seeing.

Not sure it's entirely that simple or consistent since different pulleys, S/C displacements, rotor sets (both length/width and differing twinscrew lobe-ratios) may exhibit other subtleties, but I'm thinking it's a fair general characterization of twinscrew and roots pumps (at least the gen-6 roots/TVS pump).

Seems hard to go wrong with any of them once the best combo for the intended use is dialed in ...and half the fun is getting there ...or, in my case, enjoying you all getting there!

[Vette Killer]

Originally Posted by 68fastback

VetteKiller's curves and what ShelbySteve is observing seem consistent with what I was suggesting and what the dynos Dave posted are supporting (thanks for posting those, Dave ...I didn't think to look in the dyno thread ).

With a smaller pulley the 2.9 boost curve should pull-in (relative to engine rpm) and shape-wise might look much like icemen's KB boost curve and, therefore, a HP curve that peaks within the usefull rpm range for a street engine ...at least that's what I'm thinking (and what caught Dave's eye on the 2.9).

As expected, the TVS boost curve (gr8snkbite's dyno) is very linear (simple efficient pump) so peak-Tq relative to peak-HP will be higher than with a twinscrew's non-linear (flat reverse-S) curve -- and ShelbySteve's observations seem to bear this out. This makes sense too just because the average value of an S-curve relative to its peak will always have more variation than the average of a linear curve (line) relative to its peak -- since a flat line (slope=0) exhibits peak and average at any point by definition).

With twinscrews (which just happen to be substantially larger and therefore capable of more peak boost for any given engine displacement) the peak-Tq relative to peak-HP should be lower than a roots due to that 'build-flat-build' (reverse S-curve) shape of the twinscrew boost curve -- assuming it's a universal twinscrew signature ...dunno, but suspect so. (possibly it has to do with case-compression overhead unique to twinscrews ...dunno, just a swag).

Other things being equal, I'm thinking VetteKiller's HP curve will flatten at peak (Dave's question) if the peak boost is pulleyed-in such that it start to flatten before peak engine rpm.

If the peak is pulled-in, you may then be overspinning the SC bearings at the top end (which the twinscrew manufacturers all say is no problem, but I'm not sure I believe that longterm unless the bearing mfgrs change their spec). Just the fact that twinscrews rotors must spin at different rpm creates this potential problem.

To my mind the higher *relative* Tq of the linear pump has street advantages tho the big non-linear response of the larger twinscrews are capable of big peak HP. You say po-ta-to, I say po-tah-to -lol. Two different SC 'signatures' ...at least that's what I think we're seeing.

Not sure it's entirely that simple or consistent since different pulleys, S/C displacements, rotor sets (both length/width and differing twinscrew lobe-ratios) may exhibit other subtleties, but I'm thinking it's a fair general characterization of twinscrew and roots pumps (at least the gen-6 roots/TVS pump).

Seems hard to go wrong with any of them once the best combo for the intended use is dialed in ...and half the fun is getting there ...or, in my case, enjoying you all getting there!

One other option we have been discussing is a more restrictive exhaust system...keeping the headers but going with more restrictive mufflers/cats...the off-raod exhaust and headers may be pushing the curve higher as well as there is so little (if any) restriction right now...will do the 3.0" pulley first and see where it goes; doubt I will do the lower as I don't want to machine the front cover

No matter what else I do this upgrade is going to make this so much more fun that it was with spinning the 122 with a 2.6" pulley; can't wait to feel it tomorrow and get that "this is a little scary" feeling all over again

[gr8snkbite]

thx for all the updated intel...interesting to see comparison to my rock solid tvs...which i love and shall keep...

[JTB]

Originally Posted by gr8snkbite

thx for all the updated intel...interesting to see comparison to my rock solid tvs...which i love and shall keep...

I hear ya, MC, the more I read about these install and tuning issues with KB's and The Whipples I will be going TVS for my upgraded engine topper.

[gr8snkbite]

Originally Posted by JTB Consulting

I hear ya, MC, the more I read about these install and tuning issues with KB's and The Whipples I will be going TVS for my upgraded engine topper.

cant go wrong with it...i was only shootin for 700 arena, got it..now happy.

[Birdman]

Originally Posted by gr8snkbite

cant go wrong with it...i was only shootin for 700 arena, got it..now happy.

+1 ...and with ease too not to mention with efficiency.

[gr8snkbite]

Originally Posted by Birdman

+1 ...and with ease too not to mention with efficiency.

true..it was so effortless it aint funny..even working with JL on the tune was great and a breeze..

[68fastback]

Originally Posted by Vette Killer

One other option we have been discussing is a more restrictive exhaust system...keeping the headers but going with more restrictive mufflers/cats...the off-raod exhaust and headers may be pushing the curve higher as well as there is so little (if any) restriction right now...will do the 3.0" pulley first and see where it goes; doubt I will do the lower as I don't want to machine the front cover

No matter what else I do this upgrade is going to make this so much more fun that it was with spinning the 122 with a 2.6" pulley; can't wait to feel it tomorrow and get that "this is a little scary" feeling all over again

I think headers and low-restriction cats would push boost lower but push HP higher for any given boost level. I think more exhaust restriction will reduce power but would increase boost -- since more energy will go into driving the SC and, therefore, less to the wheels. I don't think it's a problem that the 2.9 and KB have that kick-up in boost at higher rpm as long as it's translating to rwHP. If it's not, then it's going elsewhere (drive the SC). In your dyno it seems to be going to the wheels where you want it ...more exhaust restriction would be counterproductive, imo.