6100, TTspec, T2, Baja Truck only thread

MTPyle

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Our pistons are 44mm and 40mm they are pretty large. I don’t think we have time or the money to change them for SF250. They work pretty good when fresh so it’s not horrible. I already reached out to QTM who does our brake stuff to see what we have compared to what is available. They do a lot of TT brakes and should know what’s up.

Mike
 

Ikaika

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Our pistons are 44mm and 40mm they are pretty large. I don’t think we have time or the money to change them for SF250. They work pretty good when fresh so it’s not horrible. I already reached out to QTM who does our brake stuff to see what we have compared to what is available. They do a lot of TT brakes and should know what’s up.

Mike
Mike,

Using your piston measurements ( assuming you have a 4 piston caliper ) against a Jamar radial mount progressive 6 piston unit, the combined piston surface area on each of your calipers are 52.79mm......Jamar 6 piston progressive calipers are 678.27mm each.

The difference between your current calipers and the Jamar is 150.48mm increase in piston surface area for each Jamar caliper.......couple that with the increased brake pad surface area / contact patch and VIOLA.....increase in braking capacity that results in more confidence which usually translates to driving deeper into and braking later for each corner.....all this helps with getting a little closer to the podium one corner at a time.

We are using the 6 piston Jamars at all four corners in combination with 1" bore master cylinders......with proper brake pressure bias and pedal leverage ratio, this seems to be more than adequate for the 39 - 40" tire application.

Wishing you well at SF-250 !

Cheers.....
 

MTPyle

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I don’t understand your math. Haha my 44MM pistons are pretty large. I don’t see how the Jamar has 10x the surface area of our pistons. But I also have not really looked into it.

edit. The jamar has 1.5” pistons mine are 44MM is 1.75” so it’s for sure not 10x with the Jamars.

I agree more braking is better. Our brakes were really good and we could lock them up at ay time. Now not so sure.

Mike
 

jon coleman

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do a little at a time on brakes if they are tolerable( & safe), off road brakes I was told need to be ' panic sensitive' ie you dont want wheels to lock up unless you Really want them to, by Really mashing pretty hard, you dont want easy lock up, it hurts moving parts when there locked up smashing big holes& rocks and such, i did a little hydraulic math in ams/amh school , little changes in piston area can make big changes in forces applied, being in aviation your 'clued' in for sure, besides, San Felipe is no need brake kinda race from what i remember...
 

Ikaika

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I don’t understand your math. Haha my 44MM pistons are pretty large. I don’t see how the Jamar has 10x the surface area of our pistons. But I also have not really looked into it.

edit. The jamar has 1.5” pistons mine are 44MM is 1.75” so it’s for sure not 10x with the Jamars.

I agree more braking is better. Our brakes were really good and we could lock them up at ay time. Now not so sure.

Mike
Math is simple.....BUT.....I may have it wrong by assuming your calipers a (4) four piston units.

A) Choose a standard of measurement....MM or INCH and do conversions accordingly
B) Combine the total piston area for each caliper ( your caliper vs the Jamar mentioned )
C) Calculate the difference in piston surface area from one caliper brand to the next

Note: piston diameter ( radius squared ) x 3.14167 = surface area of each piston

If your current calipers are indeed (4) four piston units with 2) 44mm & 2) 40mm pistons per caliper.....( 44mm + 44mm + 40mm + 40mm x 3.14167 ) your total piston surface area is 527.80mm.

Jamar (6) six piston calipers mentioned have (4) four pistons @ 1.5" (38.10mm each ) and (2) two pistons @ 1.250" (31.75mm each ) per caliper....for a combined total surface area of 678.27mm ( 38.10mm + 38.10mm + 38.10mm + 38.10mm + 31.75mm + 31.75mm x 3.14167 )

My example IN NO WAY was to say your current set-up cannot be effective or "lock the brakes".....in fact, I'm certain your equipment is capable of what you say / describe.....the key is for the equipment to reliably and consistently have the ability to be repeatable over a wide range of conditions and temperatures to instill the necessary operator confidence to drive harder and hopefully faster.

I'm not your opposition,......I'm on your side here just trying to help sort things out.

Cheers......
 

MTPyle

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Ikaiki

thanks for the extra detailed info. Makes total sense. Like 43mod just said I think you had a typo that thru me off.

For 20% better braking the 6 piston seems worth it. And I totally agree that it will help us drive faster. Who doesn’t want to go deeper and faster. Hehe

I just don’t need this new upgrade obsession right now with all that we have been spending. Haha but I need to figure it out.

We are almost done with our major fuel system upgrade and a complete prep. It’s going well but money is flying out the door. Haha

Mike
 

Ikaika

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43mod & MTPyle.......

Thank you for catching the typo.....that boo boo changes EVERYTHING regarding calculations.....it should have read 527.80mm.

In addition, after having "proof read" that post ( after the fact ! ). I also found that in my calculations, there is a very slight variation due to using 3.1416 in the first go around vs 3.14167 in the second go.......the difference would be as follows.....527.79 vs 527.80.

Please accept my apology.

Cheers.....
 

Dezert00Taco

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Ikaiki

thanks for the extra detailed info. Makes total sense. Like 43mod just said I think you had a typo that thru me off.

For 20% better braking the 6 piston seems worth it. And I totally agree that it will help us drive faster. Who doesn’t want to go deeper and faster. Hehe

I just don’t need this new upgrade obsession right now with all that we have been spending. Haha but I need to figure it out.

We are almost done with our major fuel system upgrade and a complete prep. It’s going well but money is flying out the door. Haha

Mike
If you are already working with qtm you should look into the stop-tech 6 piston calipers when you are ready to upgrade. They will be a step way above a jamar caliper. The set up you have is pretty small for a big 6100 truck.
 

MTPyle

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We will find out Monday is the mounts are the same for the Stoptech 4 and 6 piston.

we also find out if our new fuel system will work. Haha

We are doing a variable PWM brushless fuel pump in the fuel cell. With no return or regulator. The fuel pump only runs as much as it needs to supply the right amount of fuel. So no added heat to the system or heavy load with pump running 100% duty.

really was trying to keep this under wraps, but oh well. Haha. Might as well share everything.

My hopes are it will reduce our fuel temps greatly and make it almost impossible to vapor lock. cooler fuel equals more power.

finger crossed it works. Haha

Mike
 

MTPyle

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Don’t know what that is. Haha VFD?

the LT1 has a fuel controller AKA piggy back cheater ECU. Hehe

the fuel controller outputs a PWM signal to the fuel pump controllers to manage fuel pump speed. Our new pumps are 600lph so way more than we need but will only flow as much as the ECU commands to maintain 72psi. The ECU has mapping to learn what it needs to do to maintain pressure. It’s a proven system.

this is how all new GM direct injection engines are done. So we are not doing anything crazy. Should work better than mechanical regulator

Mike
 

jon coleman

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what are/is the pick up set up like?, big filter matt? a small pickup trap door box?, it just 'floats 'inside the cell on a mount?
 

MTPyle

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The pump is hard mounted and has a Holly fuel mat attached to it at the bottom of the cell. The pump can lift and can be external so we could mount it anywhere but want it as low as we can get it in the fuel cell. We have two pumps, one for backup.

Mike
 

43mod

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For AC power a vfd ( variable frequency drive)will drive an electric motor at a constant load . Kind of like a soft start on a solar AC unit .Sounds like you have same thing in DC .
 

51rcr

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fuel line routing and you can still vapor lock. which is where it often comes from. Fresh alcohol and fuel systems are great. But most race cars it can be a nightmare. Drawing moisture into it. The chalking and plugging filters and injectors. With methanol racing sometimes in a week the alcohol would start going bad and draw lots of moisture, plug the filter. Some would drain the alky, put race fuel in and run the car and clean the filters after a race if it was going to sit for a week. Maybe you fighting alcohol issues.
 

MTPyle

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we have had these issue before we starting running E85.

One thing that I found it thats interesting. When fluid is under pressure the boiling point raises. (like a pressurized cooling system) the opposite is also true. When fluids are under vacuum the boiling point goes down. We had external pumps and the pumps had to pull the fuel out of the cell. So the input of the pump was under vacuum. This causes vapor lock at the input of the pump. Then our pumps where external and very near to our radiator. So it was hot and under vacuum. On top of that we had a regulator with a return that would return the heated up fuel back to the tank. So after an hour or so of racing the temp of the fuel in the cell is pretty hot. So its a never ending cycle that gets worse and worse as you race.

We do not have a fuel temp sensor on or system but I have heard some teams say their fuel temp can be 120 degrees or more at the end of the run before fueling. Initial boiling point of fuel starts around 95 degrees. Not only does Vapor lock become an issue but as the fuel temp increases the fuel becomes less powerful. In other words the power density of the fuel goes down. 20 degrees hotter fuel means less power.

Mike
 

Bro_Gill

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Actually, Mike, the boiling temp of gas starts at 104 degrees, but still way down. It can go as high as 392 degrees depending on blend. Maybe you should contact a fuel supplier and do some testing with different blends with established boiling points so you have a base line. This would help you define the problem easier.
 

MTPyle

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Bro

Take a look at IBU of fuels, parts of the fuels do start to “boil” or vaporize in the mid 90’s. The distillation profile curve starts under 100F.

We have ran VP, F&L, Sunoco, and pump gas. All have had vapor lock issues in our set up. Its not the fuels fault, its your system design. Our pumps, filters, and regulator is right next to our radiator. Pretty sure thats not a good set up. We have done all we can to isolate and heat shield the system but it has not worked. There is a reason no new race trucks come with external fuel pumps.

If we still have issues after our new system then I will look further into fuels, but I highly doubt we will have any issues. I actually think our new system will be an advantage over the systems used by other spec truck teams.

Mike
 

MTPyle

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Could not get the PWM variable system working with Brushless pumps. LOL

Tried really hard but it just not possible yet. Super close though. We are working with Deatschwerks and they have been amazing. We underestimate the complexity with brushless and the output signal of the GM ECM.

We were able to get the brushless pumps working with a regulator and 2 stage controller. DW custom programmed the controller to give us exactly the flow we need (300lph) for our set up on low setting then we can hit a button and put them in high setting (650lph). So at least we have a super efficient pump only pumping what we need. Trying today to get the regulator in the cell so we do not have to run fuel out and back again.

Just figured I would circle back and give a update so people dont try to do whats not possible "yet"

We gave up on the PWM late yesterday and the DW tech guy went back to the shop on a Friday night (holiday weekend) and programmed a custom controller and got it to Fedex before the 8pm cut off so we could get it today. Now thats support.

Its painful on the cutting edge. Haha

Below is a pic of our pumps mounted with the fuel mats. These are 650lph Brushless pumps that can be internal or external, so they lift as well as suck. Nice... LOL

Mike
 

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