those are some SERIOUS numbers....impressive power curves....really shows off how usable the powerband on properly setup turbo car can be....its all in the combo...
Styles RSI SC ran 144 mph no NOS and 152 mph with NOS. His car dyno'd 1050 rw hp no NOS and 1200+ rw hp with NOS. Hopefully Roof's TT will do just as well.
How come the dyno graph doesn't have such a violent torque curve like the Heffner TT? Was it tuned to have a usable torque curve down low? With Twin Turbos and a stroker on top of that I would be expecting that curve to be even more violent than the Heffner setup....but the curve looks like that of a centrifugal supercharger. [img]/images/graemlins/confused[/img]
Hope we get some more light shed on this later.
RollModel, the curve does not look to be as violent as the Heffner curve due to the sizing of the turbos. The smaller the turbo, the quicker in the RPM range the car is at full boost all other things being equal. So the properly sized turbo will have a curve similar to that of a centrifugal blower ie the boost building at a slightly slower rate due to the larger internal volume of the bigger turbos. The larger turbos can also flow more CFM of air to sustain the torque curve longer therefore the HP and TQ are much closer to being the same # since HP is a function of the torque curve. The smaller turbos hit harder with the torque peak sooner, but cannot flow the amount of air the larger ones can, therefore the torque curve of the smaller turbos is falling at a relatively greater rate as compared to that of the larger ones. This is why the smaller turbos have a greater disparity between the HP and TQ #'s.
How come the dyno graph doesn't have such a violent torque curve like the Heffner TT? Was it tuned to have a usable torque curve down low? With Twin Turbos and a stroker on top of that I would be expecting that curve to be even more violent than the Heffner setup....but the curve looks like that of a centrifugal supercharger. [img]/images/graemlins/confused[/img]
Hope we get some more light shed on this later.
RollModel, the curve does not look to be as violent as the Heffner curve due to the sizing of the turbos. The smaller the turbo, the quicker in the RPM range the car is at full boost all other things being equal. So the properly sized turbo will have a curve similar to that of a centrifugal blower ie the boost building at a slightly slower rate due to the larger internal volume of the bigger turbos. The larger turbos can also flow more CFM of air to sustain the torque curve longer therefore the HP and TQ are much closer to being the same # since HP is a function of the torque curve. The smaller turbos hit harder with the torque peak sooner, but cannot flow the amount of air the larger ones can, therefore the torque curve of the smaller turbos is falling at a relatively greater rate as compared to that of the larger ones. This is why the smaller turbos have a greater disparity between the HP and TQ #'s.
Right on the $$ I noticed in your photo you are using larger turbos also. I am surprized more turners are not trying T70's or larger. Vipers have a torque advantage most cars do not, so even with larger turbos, you should not get any sense of lag. Also larger turbos will not generate as much heat so the innercoolers can be smaller (thus more efficent) I would like to see a dyno run of a water to air cooler after driving it all day, I thought air to air was better for daily drivers.
How come the dyno graph doesn't have such a violent torque curve like the Heffner TT? Was it tuned to have a usable torque curve down low? With Twin Turbos and a stroker on top of that I would be expecting that curve to be even more violent than the Heffner setup....but the curve looks like that of a centrifugal supercharger. [img]/images/graemlins/confused[/img]
Hope we get some more light shed on this later.
RollModel, the curve does not look to be as violent as the Heffner curve due to the sizing of the turbos. The smaller the turbo, the quicker in the RPM range the car is at full boost all other things being equal. So the properly sized turbo will have a curve similar to that of a centrifugal blower ie the boost building at a slightly slower rate due to the larger internal volume of the bigger turbos. The larger turbos can also flow more CFM of air to sustain the torque curve longer therefore the HP and TQ are much closer to being the same # since HP is a function of the torque curve. The smaller turbos hit harder with the torque peak sooner, but cannot flow the amount of air the larger ones can, therefore the torque curve of the smaller turbos is falling at a relatively greater rate as compared to that of the larger ones. This is why the smaller turbos have a greater disparity between the HP and TQ #'s.
Right on the $$ I noticed in your photo you are using larger turbos also. I am surprized more turners are not trying T70's or larger. Vipers have a torque advantage most cars do not, so even with larger turbos, you should not get any sense of lag. Also larger turbos will not generate as much heat so the innercoolers can be smaller (thus more efficent) I would like to see a dyno run of a water to air cooler after driving it all day, I thought air to air was better for daily drivers.
Dan, you are correct about the larger turbos generating less heat to move a certain amount of CFM at a lower boost pressure in relation to a smaller turbo. But as far as using a smaller intercooler is concerned, I would think that the larger turbos capable of making more power would warrant a bigger intercooler. Most maniacs who want this kind of power will not be satasfied to make the same level of power at a lower boost setting. By comparison, the intercooler setup I have designed that is on my turbo car has almost double the cubic onches of volume/surface area that I had with my supercharger setup. The intercooler can never be too big! LOL! I think the air-water intercooler is a great way to go for the dragstrip with ice water, but like you say, for the daily driving deal, once the ice is used up, the intake air charge temperature will never be below the coolant temperature of around 180-190 degrees.
Great results for boost only, making over 1000rwhp is a very cool achievement and congrats to RSI.
re the differences in power curves - I beg to differ with the explanations given.
Using larger turbos does NOT make a fatter power curve, what it makes is a more violent one (other things being equal) - larger turbos will spool later but they do not spool slowly they spool quickly and when they do they move a lot more air - so you'd see less bottom end and a steep curve later in the rpm band like a cammed engine. That's what they do.
Smaller turbos spool sooner and quickly but flatten off to produce a fat power curve.
Ultra large turbos would lose bottom end and some mid range - but the top end from spool up would be ballistic.
You could soften the boost electronically and effectively detune it, but I doubt that has been the case. My guess is that the turbos are still smallish and pushing a lot of air via a bigger engine.
Whatever the case - it is working - as nobody can argue with 1031rwhp! That car should cut a great time as Sal only needed 780rwhp (on the Heffner Performance dyno) to run 147mph and 9.7. 1031rwhp should be good for high 150's trap speed.
Right now I'm comparing the dyno curve of that stroker engine to the stock engine of Sal's car after he changed to new leads and had another dyno run last night. Sal's stock engine made more torque - at 1094.8ft/lbs (corrected to 1067.7 SAE) on a fat 10.8 A/F ratio (but took more boost to do it).
HP and torque were up on the the Heffner stock engine compared with the stroker engine until around 4700rpm, then the stocker flattened off peaking at 950.6rwhp (corrected SAE 927rwhp) while the stroker just powered on from 4700rpm on up and left the stock engine behind all the way to its amazing 1031rwhp peak.
While we know there is more in the stock engine, it is never going to match the dyno power figure of the RSI stroker at the same boost.
The comparison was intersting because it illustrates how a little more boost makes up for lack of cubic inches in torque, but that better breathing and a built engine tuned right ultimately triumphs over a stock engine for power.
RSI have a great tune in that built engine and a built engine is definitely the way to go for those who want to get serious.
It would be hard to improve on what RSI have done at the boost they were apparently running. I like how the power runs right through to 5900 without dipping - that takes great breathing and a great tune. Let's now see that baby run a number at the track! :thumb:
Were the heads ported the same on Sals and the Stroker? You can't argue head flow will really influence the curve. Hard to compare these graphs whith soi many other variables. I agree with your argument that larger turbos will spool fast at the top, but remember this is not pure exponetinal function, It still is liner. The larger turbos will "soften" the blow because you are alredy above a Hp/Tq combo. Jump on the Mustang forms and look at some graphs. The power roll on will be more subtle after when it spools up at the upper end of the curve. There is also no denying the larger turbos will not generate quite as much heat, makeing for a more dense air charge.
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