info. on 91Q factory specs.

[PopPop]

Can someone please tell me compression ratios on 91 Qs motor? Also would like engine specs. sheet or send me in the right direction of where to obtain this info. Also would like to know factory differential gear ratios and stall convertors speeds!

[Jesda]

http://www.q45.org/techinfo.html

[elwesso]

(from memory)

Compression is 10.2:1Diff gear is 3.535Converter stall- 2100-2400

[PopPop]

Thanks Jesda for your tech. post very in dept. Now I need an accurate stall speed!

[zinkie13]

Just wondering....what is the stall converter speed? What does that mean? haha sorry i'm a retard

[zinkie13]

....And what does changing your stall converter speed accomplish, since I hear about people doing it every once in awhile.

[PopPop]

A torq. converter is a fluid coupling that disengages the eng. from trans. at idle. Most people even guys that have been around the block and back don't really know the value of a torque converter up grade. The first up grade anyone should make before going into the motor to make changes is to modify your converter or buy an perf. one. If you start making changes to your eng. you may gain perf. in one area, and lose in another! A tor. converter will actually more than double your torq. at take off! Stall speed you asked about is speed at which the converter slips at full throttle and this stays in effect until the engine speed catches up to the stall speed! So stall speed is (the slip). Don't just go out and buy any old perf. high stall converters. Give the person whos building your converter eng. torque, weight, trans. type, tire size, and eng. horse power, gear ratios. IF your modifying your engn. T.Q. should be on the latter end of your vehicles make over.

[MinisterofDOOM]

The first part is written assuming you're asking how a torque converter works, and not just what stall speed means. If you already know, ignore this first part, and skip to the end.

A torque converter is the automatic transmission's answer to the clutch. Since an auto transmission is always connected to the engine while driving (even between gears during shifts), no direct mechanical connection would work--the engine would stall at stops or low speeds, and shifting gears would be problematic at best. With a clutch, the mechanical connection can be disengaged. With a torque converter, a compromise is made: a fluid connection replaces the solid connection, allowing the engine to rotate with the transmission at a stop.This is accomplished by having a thick oil that is rotated from the engine side by a turbine. The transmission side turbine is then driven by the rotation of the fluids. Think of pointing one fan at another fan and turning the first on--the second fan will spin as well. The performance and torque increases mentioned in the post above this come from the fact that the blades of each turbine can have different pitch values. This means you can effectively change the rotational ratio between the engine and the transmission. In this way, an artificial "step down" can be introduced before the transmission, further enhancing the torque that reaches the wheels, especially at lower RPMs (hence the reference to a good T.C. helping launches in the post above this one).

At higher speeds, both "sides" of the T.C. match speed more closely. And at freeway speeds, most Torque Converters have a solid physical connection that locks in, thereby circumventing the additional parasitic power losses caused by the inefficient fluid connection--this is partly why freeway speeds net much better fuel milage than normal city driving would.

The requisite "How Stuff Works" article.

....And what does changing your stall converter speed accomplish, since I hear about people doing it every once in awhile.

Basically:

Torque converter stall speed is the rotational speed (in RPMs, measured from the engine side) at which the torque converter begins transmitting power from the engine to the wheels. Below stall speed, the engine can turn without turning the wheels. Once the engine RPMs reach the stall speed, power beings being transmitted normally. Higher stall speeds allow higher RPM launches--it's a similar effect to revving a manual transmission higher before engaging the clutch.
Modified by MinisterofDOOM at 1:09 AM 12/22/2005