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Celica GTs come with two different engines..the plain GT comes with a 1ZZ lump that revs to 6800....and the GT-S comes with the 2ZZ engine. They are known as "Izzy" and "Dizzy". On the rough overlay dyno chart below, you can see that Izzy rules below about 6500 in a given comparable gear. I can see times where in autocross Izzy would be faster than Dizzy...

 

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Stan said:
On the rough overlay dyno chart below, you can see that Izzy rules below about 6500 in a given comparable gear. I can see times where in autocross Izzy would be faster than Dizzy...
Yeah, but "in a given comparable gear" is the key. You wouldn't gear the two engines the same, and don't forget that the chart stops 1.5krpm short of the dizzy (I really like this izzy/dizzy slang) readline. So if you re-geared the dizzy, the crossover would be at the "equivalent" of 5krpm.
 

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Discussion Starter #3 (Edited)
>>>Yeah, but "in a given comparable gear" is the key. You wouldn't gear the two engines the same, and don't forget that the chart stops 1.5krpm short of the dizzy (I really like this izzy/dizzy slang) readline. So if you re-geared the dizzy, the crossover would be at the "equivalent" of 5krpm.<<<

I suppose one thing we can see is that compromises were necessary down low so that things worked better up high. Someone is working on a comparison taking road speed in given gears into account. In the mean time...stay on the high cam when possible!! It would be nice if Dizzy's 4-6000 range was a bit stronger, even if that weakened the extreme low end a bit. A hotter low lift cam could do this. The top end of this motor is fine from my perspective, but I'd prefer less of a jump when the second cam kicked in. In my on-the-road 2nd gear accelerometer test, the car could gain speed noticeably faster from 50-60 MPH than from 40-50 MPH. In the area of about 15%.
 

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Stan said:
I suppose one thing we can see is that compromises were necessary down low so that things worked better up high. Someone is working on a comparison taking road speed in given gears into account. In the mean time...stay on the high cam when possible!!
Agreed. I've always thought that the cam switchover point was too high. If they did it right, it should be at the point that the torque between the two cams is equal. Switching at any other point means you are not getting the most torque/hp that you could at that rpm.

However, I suspect that they need a certain amount of hysteresis to keep the engine from hunting the right cam at the switchover point. The right place to switch cams is then going to vary from track to track, depending on where exactly you need to shift and so on. Without access to a chip that lets you adjust the switchover there isn't much we can do, but do remember that all of the dyno plots only show the "high" switchover, so the tourque bump should happen lower down if you are coming at it from higher rpms rather than lower ones.
 

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if you want to go fast in an parking lot, you should just use a snowmobile and forget all that car stuff.
 

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hahaha......
 
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