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Thread: it was.

  1. #256
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    Quote Originally Posted by Andy 94SC
    Anyway, I am not so sure the HP dropoff would be due to the flow restriction of the I/C so much as it might be the fact that the I/C isn't able to cool the air as well as at lower boost levels / RPM.
    I believe you are correct sir. Flow restriction from the IC isn't always the problem but it often is. Also, looking at the intake on that Vette I don't believe that it was big enough to support that kind of HP. I could be wrong though.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  2. #257
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    Quote Originally Posted by 1FASTSC
    I disgree. But I want to ask the question....are we talking about a turbo or a super charged car?

    I want to know that answer before I disagree anymore, if it's an SC car then I don't disagree because I know squat about how SC cars and intercoolers work.
    He did say Positive Displacement. That rules out Turbo's, and Centrifugal Superchargers.

  3. #258
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    The post Charles put up for a lightning (I'm not going through pages and pages of BS to find it) showed a lightning with his blower running low boost and his blower running high boost. The low boost graph was low on torque and the high boost one had monstrous torque but the HP didn't show that kind of an increase. All the graphs I've seen for positive displacement blowers follow this pattern. Even with an M90 on an SC motor if you run low enough boost you can get very impressive top end numbers compared to your lower numbers. On an SC you could say anything you want about flow and restriction and I'd believe it but I see this trend on all the high boost positive displacement motors I've seen. Even the Cobra power band starts to move down significantly when boost is high and that really should be a high revving motor.

    I would also like to see how much HP it takes to spin a good twin screw at high rpm and boost. I've logged SC's so I can give you a pretty good idea how much our motors eat up but I can't comment on the "other" guys. Ours are not eating up as much HP as you might think. I do have a MAP of a whipple 2300 that shows power consumption at about 65hp at a 2:1 pressure ratio at moderate rpms. None of the charts go up to the 17K+ that people are taking these things to though so unfortunately I can't comment on that.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  4. #259
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    Quote Originally Posted by XR7 Dave
    So then if the problem is a lack of CFM capability, then I would expect that one would be observing a drop-off of boost at high rpm also, no?
    I forgot all about this discussion.

    No I don't think it's that bad. RPM is what keeps the boost constant so it won't drop off.

    One problem that is worked on by many drag racers that run positive displacement blowers is to find different pulley combinations to keep the boost climbing as the RPM's increase. This gets rid of the low peak HP numbers and fall off of torque.

    Don't get me wrong as there is always a base boost number that the motor sees as soon as it goes WOT.

  5. #260
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    I'm not too sure I agree on the whole air charge temperatures being more of a steep factor than CFM is. I would say that they go hand in hand if anything. If you could make an M90's intake temps 60* it would only make so much power because it isn't providing enough CFM to make any more power.

    Charles' test isn't so much of the blower's fault as it is the internals of the motor's. Of course the higher boost is going to create a higher torque number because the motor isn't a restriction to the blower at a lower RPM. Once you get to the higher RPM's then it's all about head flow/volumes. You can boost it all you want, but if there isn't enough intake volume then it wont take the boost fast enough in one big pulse.

    Air charge temps would be a compensation due to being able to regulate the timing better the cooler it gets.

  6. #261
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    http://videos.streetfire.net/player....4-03CA7C2648FC

    Big HCI 02 SS vs big cam 6.0 LS1 88 IROC http://media.putfile.com/02-SS-vs-88-Iroc

    03 Cobra with small mods vs 02 GT with 100 shot
    http://media.putfile.com/03-Cobra-vs-02-GT


    97 Cobra vs 03 350Z, short race
    http://media.putfile.com/97-Cobra-vs-350Z


    97 Cobra vs 94 Z28
    http://media.putfile.com/97-Cobra-vs-94-Z28

    Here is the 02 SS vs the 02 Lightning. The Lightning has a Forged Bottom End, Patriot Heads, Comp Cams, Whipple @ 19 PSI, 2600 stall. Was a good race!

    http://media.putfile.com/John-vs-Casey

    Some earlier races of the 02 SS and the 88 IROC, SS didnt wanna go in fourth the first run, IROC was sleeping the second run.

    http://media.putfile.com/John-vs-TJ

    The SS MOVES in fourth, ~~~~! That IROC has run 97 MPH in the 1/8 and is no slouch! We had 2 people in the IROC though but Im light riding in the IROC.
    __________________

  7. #262
    Heat and restriction all come into play, but I'm surprised the fact that efficiency of the blower itself hasn't been mentioned. Any type of artificial aspiration has its efficiency limit before you just aren't adding any more power. The OEM does a good job of sizing turbos/superchargers for the application at hand, not so much above and beyond. We can get away with a tweak here and there but nothing huge. A given supercharger of a given displacement can only flow a certain max cfm rate. Now when you start changing blower sizes even in positive displacement I DEFINATLY see a change in the curve from one blower to the other.

    EX:
    03 Cobraís/Lightning Eaton to Whipple
    Iím seeing a LOT more top end with the Whipple then with the Eaton.

    Changing 671ís to 871ís we are seeing not only torque increases but top end increases as well (depending on blower RPM). Any form of artificial aspiration can only flow so much air efficiently before you get ďpumping lossesĒ.

    I have also seen something similar to this with Nitrous Oxide. We get to the point where we simply just canít cram any more in and out of the cylinder and the vehicle starts to loose power even though we are putting more into it.

  8. #263
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    Quote Originally Posted by CarlisleLandOwn
    I have also seen something similar to this with Nitrous Oxide. We get to the point where we simply just canít cram any more in and out of the cylinder and the vehicle starts to loose power even though we are putting more into it.
    yep..have also run into this problem..but not really losing power. My buddys car (the ones i posted the vids of) runs a dry kit, and was going consistent 10.30's with a .098 jet. We eventually went to a .102, didnt pick up anything at all.. started drilling that jet until we had it at about .110 and it still would not pick up anything.

  9. #264
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    Car Craft did a test one time where they took a basic small block motor and put increasing amounts of nitrous on it till it blew. They got to about 250hp when they apparently ran into that problem. The nitrous started backing up in the intake and it blew up the carburator or something. They decided that they had reached the limit with that combination of what the motor could ingest.

    Blower efficiency it certainly an issue and it has two fronts from where I see it.

    1) at a certain rpm the VE of the blower starts to fall off badly. This would be due (I assume) to air velocities in the ports and around the rotors.

    2) power consumption due to a non-linear increase in drag as rpm increases.

    I've seen graphs for some of the blowers but none of them extend into the rpm ranges that we are taking these things. Funny how the manufacturer's charts all stop several thousand rpm lower than what we are running them.

    Maybe it is more about blower efficiency than IC efficiency. I made the connection because I've logged the air temps of many SC motors and I've seen a direct correlation between temps and power output. People who spin their blowers very fast will also show steep increases in temp above (in our cases) 4500rpm which also matches the power fall off of most SC motors.

    However, I am also willing to accept that my observations may be more the reflection of two paralell conditions and not so much cause and effect. For us the way to find out is to run the biggest blower we can find vs. the same blower in a smaller displacement at the same boost levels. I will be doing this but not tomorrow or next day. It will take a little time to put the puzzle pieces together.

    We are lucky in this regard because we have the option of running a much bigger blower compared to displacement than the "other guys" can. I can put a 2.6L on an SC motor and compare the results to that of the 1.7L. We'll have to see what happens.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  10. #265
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    North Georgia
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    766
    Quote Originally Posted by XR7 Dave
    Car Craft did a test one time where they took a basic small block motor and put increasing amounts of nitrous on it till it blew. They got to about 250hp when they apparently ran into that problem. The nitrous started backing up in the intake and it blew up the carburator or something. They decided that they had reached the limit with that combination of what the motor could ingest..

    call up NOS/holley and ask what the maximum nitrous amount to use on your motor is. 10-1 they give you the same answer they told me


    "keep jetting it til it blows up, then back it off 50hp"

  11. #266
    Quote Originally Posted by Blown 91 Bird
    yep..have also run into this problem..but not really losing power. My buddys car (the ones i posted the vids of) runs a dry kit, and was going consistent 10.30's with a .098 jet. We eventually went to a .102, didnt pick up anything at all.. started drilling that jet until we had it at about .110 and it still would not pick up anything.

    There is a reason for this. You can only get soo much fuel from bumping your fuel pressure. Afterthat you won't supply enough for proper combustion and it will no longer increase hp.

    Quote Originally Posted by XR7 Dave
    Car Craft did a test one time where they took a basic small block motor and put increasing amounts of nitrous on it till it blew. They got to about 250hp when they apparently ran into that problem. The nitrous started backing up in the intake and it blew up the carburator or something. They decided that they had reached the limit with that combination of what the motor could ingest.

    Blower efficiency it certainly an issue and it has two fronts from where I see it.

    1) at a certain rpm the VE of the blower starts to fall off badly. This would be due (I assume) to air velocities in the ports and around the rotors.

    2) power consumption due to a non-linear increase in drag as rpm increases.

    I've seen graphs for some of the blowers but none of them extend into the rpm ranges that we are taking these things. Funny how the manufacturer's charts all stop several thousand rpm lower than what we are running them.

    Maybe it is more about blower efficiency than IC efficiency. I made the connection because I've logged the air temps of many SC motors and I've seen a direct correlation between temps and power output. People who spin their blowers very fast will also show steep increases in temp above (in our cases) 4500rpm which also matches the power fall off of most SC motors.

    However, I am also willing to accept that my observations may be more the reflection of two paralell conditions and not so much cause and effect. For us the way to find out is to run the biggest blower we can find vs. the same blower in a smaller displacement at the same boost levels. I will be doing this but not tomorrow or next day. It will take a little time to put the puzzle pieces together.

    We are lucky in this regard because we have the option of running a much bigger blower compared to displacement than the "other guys" can. I can put a 2.6L on an SC motor and compare the results to that of the 1.7L. We'll have to see what happens.

    Dave, all of the above are conditions that will lead to power loss. As you know itís a balancing act and Ford never intended for these motors to make as much power as we are building them to. If you don't solve ALL the issues at hand it will still never be correct and the desired result will never come forward.

  12. #267
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  13. #268
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  14. #269
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