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Yeah I think the video is Tim pumping the accelerator rather than surging.

Surging is not a good thing to have. It's usually an indication of a lean condition caused by improper air/fuel ratio or a vacuum leak and can destroy an engine.
 

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Yeah I think the video is Tim pumping the accelerator rather than surging.

Surging is not a good thing to have. It's usually an indication of a lean condition caused by improper air/fuel ratio or a vacuum leak and can destroy an engine.
I don't know... Here is what he said in the BS area thread:
http://www.stevesnovasite.com/forums/showthread.php?t=99917&highlight=blower+surge
With the ECU set the way I have it running a 4speed It will clean up a little when I push in the clutch. And start up again when you put a load on it. The fuel I get with the surge help keep it a little cooler. I can tune it all out but it run just a little hotter. So I went with more fuel to keep it cool.


Is blower surge harmful? Is that part of what causes them to explode sometimes? BTW thanks for that link GMpartsman
 

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The increase in RPM always comes from a lean condition. When you have an over-rich condition, the RPM drops. Thus, when you have a surging problem (which is not good) you have a lean condition occuring at some point in your induction. This is true whether you are running a blower or normally-aspirated.

A supercharger can cause the engine to surge if the boost pressure is varying. High-boost setups are more prone to boost surge. I don't think Tim is using a lot of boost so his problem was probably more related to his fuel injection setup.

Surging is not good although it's a lot more harmful to have it happening at higher RPM than at idle.


What makes the blower "surge"?

This is caused by a rich/lean cycle at idle. As the motor leans out, the RPM's increase and richen up the motor, when the motor richens the RPM's decrease and the motor leans out again. This continual cycle is known as "blower surge". With proper tuning, some of this surging should be able to be eliminated.

http://www.theblowershop.com/faq/10
 

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The increase in RPM always comes from a lean condition. When you have an over-rich condition, the RPM drops. Thus, when you have a surging problem (which is not good) you have a lean condition occuring at some point in your induction. This is true whether you are running a blower or normally-aspirated.


What makes the blower "surge"?

This is caused by a rich/lean cycle at idle. As the motor leans out, the RPM's increase and richen up the motor, when the motor richens the RPM's decrease and the motor leans out again. This continual cycle is known as "blower surge". With proper tuning, some of this surging should be able to be eliminated.

http://www.theblowershop.com/faq/10
Thanks... Guess I don't want surge after all. Oh well.:D
 

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If you ever listen to a top fuel dargster or funny car being shut down, the rpm's go way up before the motor actualy shuts off, it's because they cut the fuel to the motor, and as it leans out the rpm's rise until there's no more fuel in the motor.
 

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had a couple of blown motors several years ago,
both pulsed on idle like the s10 video,
never hurt either engine but then they were both fairly mild,
nipped a few spark plugs though before i found out i had too much timing:eek:
 

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From my experience, the surge is caused by how tight the blower is set up. Mooneyham, littlefield and certain BDS blowers will do this. Obviously for the street they dont set them up too tight do to the added heat in the blower. When were tuning up a blower motor if you add more idle fuel it will surge more, lean it out and it will smooth out. Most of our customers ask for the surge but if the blower isn't tight enough you wont get it to surge.
 

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"Lean" Is one I had mine set to lean for shows " People Like to hear it that way"
As for mine not being consistent. It is were the ECU is trying to over come the setting I have set.
Number two Mine is not a street Blower It is a race unit. Not the best one for street but I had a plain and that was the only way to get there was with it.
I wanted to see just how fast I could get a Roots Blower on the street and really be able to drive it. My intake is a one off that me and a friend made for my car and the cam is a one off that was made by Comp Cam to my Specs. A guy I know at Comp was great at helping with the cam as he was like me " Lets try this and see what it does" It took three try before we came up with this one.
On the down side running a race blower I have to tare it down ever winter and rebuild it. My car has been a great tool to find out lots on Blowers air flow what will work and what will not.As for the Surge It will not hurt one up to a point but going lean it not always a good thing. Most Carbed Blower cars have a very hard time getting it out. But with the EFI setup it is no big deal. I hope this will help you out some.
 

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One more thing. As for pumping it " I do not think I would like trying to go around at a Good Guys show pumping it I think my ankle would give out.
And mine has no more Surge as I found out the hard way running lean on a Blower is not a good thing. Cost me a case.
 

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How much boost are you running? I have a BDS Stage III 8-71 which has Teflon strips but not as tight or as high-maintenance as a race-only Stage IV blower which requires a tear-down every year. I'm going to under-drive it for the street but it will be setup for maximum performance on pump gas.

You can get 12 lbs. boost from a street blower without Teflon seals on a small block which would be more than most could handle on the street and still be able to run pump gas.

I guarantee you that I will be doing everything I can to get rid of any surging. I don't want it. When running "street" boost levels it's a sign of poor tuning.
 

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On the high side we went up to 25lb and the the fun started. lots of broke stuff Rods Pistons took the side out of a block push rods you name it I broke it. Pulled the Boost down to 20 and then we started making power. But on the street I am running under drive pulleys and I only make around 12. I only run pump gas and the car does great. BDS and Moon tell me I need to get it down to around 8 and it would run a little cooler. But I do not think it will with the cam I am running.
 

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How much boost are you running? I have a BDS Stage III 8-71 which has Teflon strips but not as tight or as high-maintenance as a race-only Stage IV blower which requires a tear-down every year. I'm going to under-drive it for the street but it will be setup for maximum performance on pump gas.

You can get 12 lbs. boost from a street blower without Teflon seals on a small block which would be more than most could handle on the street and still be able to run pump gas.

I guarantee you that I will be doing everything I can to get rid of any surging. I don't want it. When running "street" boost levels it's a sign of poor tuning.
You should be able to go about 3% under and be fine on pump gas. That I what I am running now. With Carbs you may be able to sneak up a little more than that buy pulling some timing out.
 

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Do you have a BDS blower? I have a big block so I should be able to get away with more drive ratio on pump gas than a small block would with the same blower. I'm going BDS EFI too so I'll be needing to draw on your experience when it comes time to dial it in.

Here's my cam:

Isky Mechanical Roller (Special BDS grind model 4500R) Lift: .714/.714, Duration @ .050: 284/292, Adv. Dur.: 318/322, 110 Lobe center
 

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Like 3DTIM's car: http://smg.photobucket.com/albums/v326/Highmark/?action=view&current=3c831ce7.flv

I did a search and found nothing.:no: So what causes it? Fuel mixture too rich? Cam specs not matched to the rest of the combo? Sorry but if I ever went the supercharged route I would love to have some surge:D
That's the coolest thing about having a blown alky deal. the "rump...rump...rump..." neither good nor bad. I don't know anything about how to set up a blown alky deal but I can find out. It can be adjusted out but why? people at car shows flock to blower cars like bees to honey. I think its the way the fuel is being delivered on the idle circuit and it tends to be on the rich side(eyes burning and back of throat) you get used to it. I used to help out my buddy leonard that had a 62 wagon that was blown on alky.
 

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That's the coolest thing about having a blown alky deal. the "rump...rump...rump..." neither good nor bad. I don't know anything about how to set up a blown alky deal but I can find out. It can be adjusted out but why? people at car shows flock to blower cars like bees to honey. I think its the way the fuel is being delivered on the idle circuit and it tends to be on the rich side(eyes burning and back of throat) you get used to it. I used to help out my buddy leonard that had a 62 wagon that was blown on alky.
Alky is not like gas. Lot more fuel and burns a lot longer. It is great until you have a fire. I can make tons more power with it but and not afford it. You can go through $200 on fuel in a day just cursing around. E85 makes great power to but can not get it around here.
 

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Do you have a BDS blower? I have a big block so I should be able to get away with more drive ratio on pump gas than a small block would with the same blower. I'm going BDS EFI too so I'll be needing to draw on your experience when it comes time to dial it in.

Here's my cam:

Isky Mechanical Roller (Special BDS grind model 4500R) Lift: .714/.714, Duration @ .050: 284/292, Adv. Dur.: 318/322, 110 Lobe center
You will make great power with that cam and sound real good. When you get ready let me know. You do know that your ECU comes with no tune in it. You going with the 8 injector or 16 with your setup? Have you bought it yet if not let me know. I know a guy you may want to talk to.
 
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