Why you would NOT upgrade your turbo

[Killerbee]

http://members.cox.net/td-eoc/compression spreadheet.xls

I have come to some initial conclusions, but if you look at what happens when you increase boost or IAT, you get eye-popping realities.

For example, going from 20 to 40 psi of boost (20 psi increase) increases TDC compression by 1000 psi, a 50 fold impact.

A 50 deg temp increase due to the lower efficiency of higher compression, means going from an IAT of 150 to 200. This increases compressed temp 4 fold, from 1450 to 1620F.

I did this in a quest to determine how turbocharging kills motors, and it becomes obvious. It also lends a strong argument to N2O (not a fuel), which lowers charge temp, and doesn't increase cylinder pressure before combustion like a turbo does.

Open for discussion.

 

[IdahoRob]

Good post. But CP is power and air helps use the fuel and I like to go FAST. Thoughts on a twin setup where both chargers are in there MAP?

I do have a hard time believeing that N2O does not increase CP, but I'm just a dumb brick layer. How would N2O increase HP by as much as 500HP if there is no increase in CP?

 

[super diesel]

and doesn't increase cylinder pres...not till the detonation of the injected fuel?

 

[Dzlnut]

Good post. But CP is power and air helps use the fuel and I like to go FAST. Thoughts on a twin setup where both chargers are in there MAP?

I do have a hard time believeing that N2O does not increase CP, but I'm just a dumb brick layer. How would N2O increase HP by as much as 500HP if there is no increase in CP?

Dumb Brick layer may ass......

 

[Killerbee]

Yes, this is all pre-ignition. And doesn't address peak CP after ignition. But it is safe to say that the lower the initial TDC temp and pressure (spreadsheet), the lower the peak will will be.

This opened my eyes, and I just became more aware of some realities that I wasn't aware of before. Serious boost pressure means serious stress. I never really appreciated this before.

N2O makes more power without increasing the pressures during compression. Yes, there is more peak CP post-ignition, because there is more oxygen without more boost.

What is also under-appreciated is that IAT2 goes up steeply with increased boost. This adds a double whammy of added thermal stress to the mix. N2O OTOH brings this down, instead of up.

That's my interpretation.

 

[McRat]

The first "fast" Dmaxes were all bottle fed. Nearly all of them blew up. Many under 600rwhp.

Then came big chargers, and engines blew up too.

I guess is just depends on which way you like blowing them up.

 

[McRat]

There have been some very successful trucks running the OEM charger + drugs, Spruill comes to mind.

It is still a workable combo, but will not stop the need for rods. No engine I'm aware of survived a 200hp shot for very long.

 

[malibu795]

cant make HP with out CP
cant go any were with out TQ

killing any one of those three factors you slow down period.. now one could make "X" CP more effective.. but it will still be at TDC

 

[McRat]

cant make HP with out CP
cant go any were with out TQ

killing any one of those three factors you slow down period.. now one could make "X" CP more effective.. but it will still be at TDC

Wendy, Casper, and Blue all have the same torque within 100ftlb. Which one do you think will pull a sled further?

 

[Killerbee]

ok, trying to back up a step.

We all agree that all positive cylinder pressure that occurs prior to TDC, is working negatively, to turn the motor backwards. Minimizing this "negative torque" while maximizing the positive torque (explosion) is how power (and torque) are maximized with minimum possible damage.

Anything that cools charge, also increases density without the usual pressure increase. Also, torque and power are proportional to the difference between the TDC pressure unignited, and the peak CP after ignition. Obviously, this difference is least damaging when it starts out as a low number, instead of a high one.

Winging it here.

 

[McRat]

Yes, on paper it sounds right.

In practice, it doesn't appear to work.

 

[malibu795]

Wendy, Casper, and Blue all have the same torque within 100ftlb. Which one do you think will pull a sled further?

you put the same shift points and gears in all 3 trucks

have you gotten the same boost on a dyno that you have at the track yet pat?

if they were all the same.. they would calc out with same hp/tq @ the 1/4 given weigh differnce.

 

[McRat]

Why would the shift points matter, if torque is King? Torque has no RPM component to it.

 

[Killerbee]

Yes, on paper it sounds right.

In practice, it doesn't appear to work.

not to argue, but it appears that in practice, a bigger turbo does get you closer to insuring demise.

So, I am thinking, and feel free to disagree, that the "safest" way to make big numbers, is keeping boost "reasonable", cooling charge, and adding oxidizer.

 

[McRat]

not to argue, but it appears that in practice, a bigger turbo does get you closer to insuring demise.

So, I am thinking, and feel free to disagree, that the "safest" way to make big numbers, is keeping boost "reasonable", cooling charge, and adding oxidizer.

So 700hp on nitrous is 100% failure rate, and you're saying big charger is what, 115% failure rate?

 

[Killerbee]

I have no idea, you are the practical master.

I am learning from you guys.

 

[malibu795]

Why would the shift points matter, if torque is King? Torque has no RPM component to it.

casper doesn make ~1000lb at the place that wendy or blue does..

 

[McRat]

Here's what is looks like to me. Our first engine bent it's rods at 750hp. It was never sprayed at high boost level. Pistons were virgin, and were reused. Two other western trucks bent their rods on nitrous + stock charger at similiar HP levels roughly the same time. If I understand it right, pistons were intact on those trucks as well.

I built an engine with Crower rods and LBZ pistons, and ran the same turbo setup, and same HP. All was fine until I sprayed it, then compression fell. It ate the pistons.

Next engine was a bigger charger, 800hp, and lost compression as soon as I sprayed it. We ran the engine anyhow at Bonneville, even though compression fell from ~350psi, to 320-250psi. The engine ran fine at Bonneville even with the hurt pistons (no bottle) but succumbed to high piston temps.

Obviously, I don't have much faith in big boost+nitrous anymore. It would be tricky to spray 300hp shot into a charger that tops out at roughly 500hp. The chargers tend to die when spraying that hard. 1000hp has been done with fuel only, but nobody has done that with a stock charger + drugs.

So if you are looking for up to 650hp, you can get by with a stock engine on fuel or nitrous. 750+ is going to require rods most likely, and will take a big charger(s) anyhow.

 

[McRat]

casper doesn make ~1000lb at the place that wendy or blue does..

Casper is faster, quicker, and dyno's higher with 1100ftlb than it did with 1580ftlb.

Torque is only a useful number when used with RPM. Torque & RPM is horsepower, so as soon as you mention MPH or RPM, you aren't talking about torque any longer, you are actually using HP.

Kinda like if I tell you a trap speed speed, and you need to figure out HP. Without weight, you can't tell what is needed.

Yes, I know the Dodge Boards disagree with my "theories" concerning torque, heck, some magazines even downplay HP. But it seems that using more horsepower (regardless of what the torque numbers are) has always made me go quicker.

 

[Killerbee]

does anyone use dsp switch to temper timing for N2O?

I have thought about it, I wonder if there is a way to institute an automatic timing retard with spray actuation.