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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Tue Nov 10, 2009 4:43 pm 
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Using pump gas for racing is not the best thing. Pump gas changes from season to season and from one location to the other in order to make low compression stockers start and run correctly etc. AV-gas is a consistant fuel that is the same everywhere in the world and its the same all year and it evaporates easily inside the engine to create a good homogenous mixture throughout the cylinder. Av-gas has just about the highest energy content of any petrol, racing fuels or not. Race fuels are made from av-gas. Av-gas is the stuff to use. I dont understand why people wont tune to run it. It tunes to run nice at light load to keep cylinder condition correct for changes to WOT. Its easier to idle on the line with it. It is far more forgiving of a bad engine combination than street unleaded is. Its cheaper than race fuels. If a person has to race with street unleaded because of the cost then they are racing in a class outside their budget and that's never a good recipe for success in a class.


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Wed Nov 11, 2009 11:50 pm 
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Well, after a long day of frustrations getting the engine on the dyno (not real happy about the exhaust arrangement here) and then running many tests, I'm tired but the results are in.

The most it showed on any pull was 634HP @ 6900. The power was above 600 for nearly 1500rpm (6000-7500). The power just doesn't want to drop. The TQ pk was 527@ 5300 and was still 525@ 6000. This was with 92 octane BP pump gas with a mix of 5gals pump gas to 0.5gals race gas. Avgas showed similar power.

I'll post more details later this week if anybody is interested. I got the files from all 17 pulls from the WinDyn software and found a dyno file viewer program that is a free download on SF's website so I can study the #'s in more detail.

Rick360 wrote:
Any guesses as to HP and rpm? Closest will get a gift cert for the sum total of $.01

randy355 wrote:
I'll make a guess of 627 @ 6600 rpm
Randy would have won the gift certificate except the rule about contest winners can't be related.

Rick


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 12:13 am 
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rick360 wrote:
The power was above 600 for nearly 1500rpm (6000-7500). The power just doesn't want to drop.


This is an interesting part of the results.

Learning what makes an engine hang on to the power past peak HP, and have that flat power curve up around peak hp, and past peak HP, would be of value.

Any Ideas on that?

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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 1:36 pm 
 
rick360 wrote:
Avgas showed similar power.

You must have access to that low altitude compensation fluid with the high RPM additive. This is nuts. Naturally, we all know several people who won't use AvGas in their cars for various superstitious reasons, but now I have met several airplane guys who want to use car gas because AvGas is "too high octane". Idiots. [-( I will not ride in any of their kamikaze machines.


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 2:14 pm 
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rick360 wrote:
I'll post more details later this week if anybody is interested. I got the files from all 17 pulls from the WinDyn software and found a dyno file viewer program that is a free download on SF's website so I can study the #'s in more detail.



http://www.superflowtechnologies.com/Da ... loads.html


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 4:47 pm 
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Tuner wrote:
rick360 wrote:
Avgas showed similar power.

You must have access to that low altitude compensation fluid with the high RPM additive. This is nuts. Naturally, we all know several people who won't use AvGas in their cars for various superstitious reasons, but now I have met several airplane guys who want to use car gas because AvGas is "too high octane". Idiots. [-( I will not ride in any of their kamikaze machines.


Yes, I've heard of the superstitions regarding avgas. "Made for high altitude", "Its too dry" etc. I've used it in the past on sbc's up to 13:1. On the 13:1 engines I was able to gain power using race gas AND increasing spark advance.

I am only using pump gas because of the cost. It was $4.95/gal for me to try. 92 pump gas is ~$2.79. I like mixing in a pinch of race gas for the lead. It has proven consistent in the past for me this way if you're not pushing the timing.

randy355 wrote:
This is an interesting part of the results.
Learning what makes an engine hang on to the power past peak HP, and have that flat power curve up around peak hp, and past peak HP, would be of value.

Any Ideas on that?

I think on this engine (and probably most engines) it is due to the intake manifold size. How much taper and volume the runners have in the intake manifold has a big effect on power after the peak. I've heard the exhaust having a lot more duration can do this too, but my ex has only 5º more duration.

Rick


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 5:34 pm 
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When the oil companies list up the distillation temps for fuels that doesn't tell all the story. Its a bit like cylinderhead flow CFM, the racers have to have something to talk about. If you look at AV-gas distillation specs you see its high temp stuff, but it evaporates readily when you toss it on the ground. Toss street unleaded on the ground and compare it to AV-gas. Wash some parts in street unleaded or av-gas, see the difference. Blow the duster gun from the compressor onto street unleaded and then av-gas. Any old school racer has done what I'm saying and will know that's why people need to use av-gas. You have to tune differently for it and you have to setup the carby emulsion etc because its lighter density than other fuels but its the best fuel for consistency. Most hotrod engines don't have enough compression time, (note 'time' not ratio) so a fuel that evaporates better (av-gas) helps.


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Thu Nov 12, 2009 10:28 pm 
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So would you say the evaporation rate makes it possible to evaporate in the runners and ports instead of hitting the compression, where it makes it harder to evaporate? Fuel suspension is why port and runner shape is so important, right?

Will it use more AvGas than a high octane car Cas? Another question I would have is unit to unit, how do BTU per unit compare?

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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Fri Nov 13, 2009 12:32 am 
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rick360 wrote:

randy355 wrote:
This is an interesting part of the results.
Learning what makes an engine hang on to the power past peak HP, and have that flat power curve up around peak hp, and past peak HP, would be of value.

Any Ideas on that?

I think on this engine (and probably most engines) it is due to the intake manifold size. How much taper and volume the runners have in the intake manifold has a big effect on power after the peak. I've heard the exhaust having a lot more duration can do this too, but my ex has only 5º more duration.


I think one other thing that helps this, is the wider pushrod area of the track 1x heads. Even more so on that cube of engine.

The av gas test didn't surprise me. A little more timing may have helped the av gas.

My opinion on fuel is, the only time power is to be gained is if it's oxegenated vs non oxegenated, or the current fuel won't allow best ignition timing.

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Randy


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Fri Nov 13, 2009 3:10 am 
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Bubstr wrote:
So would you say the evaporation rate makes it possible to evaporate in the runners and ports instead of hitting the compression, where it makes it harder to evaporate?

Whether the fuel vaporizes in the intake or not has influences upon the final achievements in the cylinder. Some concentrate on the simple idea that gassing the fuel in the intake reduces the VE of the engine but there is more to it than that. Its what happens inside the closed chamber that matters and a little gas in the intake that stays at ignition arc time is sometimes beneficial.
Quote:
Fuel suspension is why port and runner shape is so important, right?

Thats where the interlinking comes in, the air flow and the fuel suspension and the evaporation of the fuel interlink in the result of whats present in gas form at the closing of the intake valve and start of compression. Valve size and vacuum created during the fuels travel around the valve etc vaporizes the fuel, different fuels react with different results in this part of the cycle. The thing about av-gas is it does evaporate well so it can work in a large range of engine combinations and it has high octane to stop detonation that may happen from over heating the gas molecules. The chamber is a balance of opposing ideas it seems, on one hand you need a gas state to burn but on the other hand you dont want to compress the gases too long. These things are not evident in a distillation test.
Bubstr wrote:
Will it use more AvGas than a high octane car Cas? Another question I would have is unit to unit, how do BTU per unit compare?

Av-gas is lighter density than other fuels so it needs bigger jets so the volume consumption per mile is higher but its heat output per Kg is greater than other fuels so it evens out a bit. How it works for each situation is up to far more variables than just theory. Avgas is very similar in distillation to VP MS101, but its cheaper. Avgas has 44 Mj per Kg heat energy, other fuels are not as easy to find the values for. But street unleaded is less than avgas, but you would have to find out what it is for your area as it varies all over the planet.


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Fri Nov 13, 2009 3:53 pm 
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rick360 wrote:
Rick360 wrote:
Any guesses as to HP and rpm? Closest will get a gift cert for the sum total of $.01

randy355 wrote:
I'll make a guess of 627 @ 6600 rpm
Randy would have won the gift certificate except the rule about contest winners can't be related.


What a bummer!!! :-({|=
I had BIG plans for that gift certificate!!!

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Slow racing is better than no racing!

Randy


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Sat Nov 14, 2009 11:43 pm 
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Here are the numbers from one of the better pulls.

Rick

RPM . . Torque . HP
5000 . . 520.0 . . 495.1
5100 . . 524.3 . . 509.1
5200 . . 527.2 . . 522.0
5300 . . 527.8 . . 532.6
5400 . . 523.8 . . 538.5
5500 . . 522.9 . . 547.6
5600 . . 522.0 . . 556.6
5700 . . 520.7 . . 565.1
5800 . . 518.2 . . 572.2
5900 . . 524.6 . . 589.3
6000 . . 525.4 . . 600.2
6100 . . 516.7 . . 600.1
6200 . . 514.2 . . 607.0
6300 . . 507.6 . . 608.9
6400 . . 507.8 . . 618.8
6500 . . 502.3 . . 621.7
6600 . . 494.2 . . 621.0
6700 . . 493.3 . . 629.3
6800 . . 483.5 . . 626.1
6900 . . 482.9 . . 634.4
7000 . . 472.1 . . 629.2
7100 . . 464.5 . . 627.9
7200 . . 457.9 . . 627.7
7300 . . 455.0 . . 632.5
7400 . . 442.7 . . 623.8
7500 . . 427.7 . . 610.8

Best jetting, 36deg T, 2" headers, vac pump on, pump gas 92 (10:1 blend w/112 sunoco)


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Sun Nov 15, 2009 12:16 am 
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Looks like it could have been pulled to a little higher rpm. Might be a little susspect of that 7500 rpm number, not pulling it higher.

What are you thinking for stall speed, if low et was most important? I'm thinking 6300-6400 rpm.

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Slow racing is better than no racing!

Randy


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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Sun Nov 15, 2009 6:49 pm 
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Nice power #'s for a truely pump gas friendly engine!! =D>

Honestly I'm surprised that the power is hanging on that long. I figured it would have been done and dropping sharply by 7000. Did you also do any work to the heads?

Scott

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420 SBC 1.085, 4.85@140.5, 7.67@172.7
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 Post subject: Re: Dynoing my 414ci SBC
 Post Posted: Sun Nov 15, 2009 9:54 pm 
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358t wrote:
Nice power #'s for a truely pump gas friendly engine!! =D>

Honestly I'm surprised that the power is hanging on that long. I figured it would have been done and dropping sharply by 7000. Did you also do any work to the heads?

Scott

Thanks Scott.
Yes, the heads (Brodix Track1X) were ported by me also. Flowed ~ 310@.600" and 315 @ .700" w/2.10" valve.

Rick


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