Im just curious where you guys are shifting at. I did a few searches on here and was comparing dyno graphs and seems like the power starts to fall off around 5800 rpms even with this cam. I didnt see a whole lot of dyno graphs posted so if any of you have some input on this please let me know. I usually shift mine around 6200 rpms. Do you guys think this is to high?

 

Anyone???

 

I would say shift at 6100 at most. But probably 6000 will be better... just experiment at the track and compare the results. Also keep in mind that the stock tach is about 200-300 rpm off. (shows more than actual)

 

Yeah, I noticed that when my buddy used his laptop to scan my car. I was shifting at 6400 by the rpm gauge but on the scan tool it was showing 6100-6200. Thanks for the info man!

 

There are 2 things that will cause you to shift to the next gear.

1) You run out of RPM capability of the valvetrain/bottom end.

OR

2) Your TQ in the next gear is higher than the TQ in your current gear. (taking into account the gear ratios in your tranny)

This happens when the TQ falls of so quickly, like in a stock LT1. There no reason to shift above 5800 RPM or so in a stock LT1 because the TQ starts falling off so quickly that it's better to shift to the next gear where you are in the max portion of the TQ band. With the dyno sheets of the 224/230 that I've seen, you want to spin it up as high as the engine can handle it. The TQ band on the 224/230 is broad and goes up high in RPM. You will get the best times shifting as high as you can without damaging parts. Depending on the parts that you have, and knowing that the 224/230 is a XE grind, you have to be careful how far you spin it up, but I would think 6200 RPM is o.k. By the way, max HP has nothing to do with where you should shift. It's all about the TQ curve.

If you have a dyno sheet of your car, I will show you what I mean.

Dan

 

Thanks man.

I do not have a dyno sheet of my car yet. After I get the long tubes and duals put on next week Im gonna have it dyno'd. I will post the numbers then.

 

On the dyno, my setup with heads looked like it was going to peak at about 6000 RPM. It was really flattening out at 5800, so about 6000, 6200 max for the peak. Shift would have come in the area of 6200-6400 at most.

 

I've taken mine all the way to 6500. It seems like it just wants to keep going past 6000 so easy. I have the LT4 conversion so I don't know if that matters.

 

By taking the gear ratios of the tranny into account, you are following the HP curve--you're just doing a bunch of unnecessary math to get there. By changing your #2 to "Your HP in the next gear is higher than in your current gear" you will come to the same results without doing a bunch of unnecessary math which increases the chances of errors.

 

6200

 

I thougth 6200 was the sweet spot. Thanks guys!

 

Argh, I've been through this too many times before. You are not following your HP curve when you accelerate. You follow the TQ curve. Gears multiply the TQ to the wheels. HP is a function of TQ. You want to maximize the TQ that you put to the wheels in each gear. Looking at HP just makes things more difficult because you will always have to bring the calculations back to TQ.

You can't look strictly at HP.

Dan

 

Yeah I used to turn my Hotcam 6500+RPMs and it liked it at the track. A general rule of thumb is to turn a engine 4-500rpms beyond pk HP if everyhting is working correctly. Now every engine is different but it has always worked for me at the track. Later Clint

 

I guess you just haven't been through it the right way before.

Quote:

You want to maximize the TQ that you put to the wheels in each gear.

It's so simple...torque at the rear wheels at any given speed is Horsepower. It's on the graph right in front of you. Why calculate it again and call it something different?

Quote:

Looking at HP just makes things more difficult because you will always have to bring the calculations back to TQ.

No, it's easy because all the calculations have been done for you.

Quote:

You can't look strictly at HP.

Yes you can. And you should. I'll show you. Take my old dyno, for example:

http://www.jonaadland.com/NewPics3/Baseline.JPG

Let's consider the 3-4 shift. If I shift at 5900, that puts me just over 4500 after the shift. I've got 280 RWHP before the shift and 280 RWHP after. There. Done. No math. No torque.

Let's try it your way: If I shift at 5900, I have 250 RWTQ, which is equivalent to 250*1.3/1=325 in the next gear. What do I have in the next gear--just over 4500? You guessed it, 325. Same difference, more math, more room for error.

The important math has already been done for you. It's called Horsepower.

 

You just forgot one important thing which he was trying to explain to you. The gear ratio of the tranny(I cant remember third of the top of my head but fourth is 1:1 so thats easy, however in third you will have to multiply the torque at the shift point by the gear ratio to get the actual torque). Whoops guess you missed that one!

Don't be ******* to someone trying to explain something right!