I am looking for a starter for my small Chevy. CSR says the 6:1 ratio starter will spin the engine faster than their standard 3.75 gear reduction unit up to 11:1 compression. Seems backwards to me. I want something to spin the engine fairly fast to help reduce the priming time of a belt driven fuel pump. Can anyone shed some light on this??
Thanks
Jay
Mini starter question?
Moderator: Team
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bracket boy
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Cobra
I have checked the CSR catalog and nowhere do they say that a 100U will spin an engine faster than a 100. They do state that a 100 is good to 450CI and 12.5:1 compression and the 100U is good to 454CI and 11.1:1 compression. Increasing gear ratio on a starter increases available torque at the expense of RPM.
There are two important, distinct phases, in starting an engine, with any type of starter motor..........
The first is the "Breakaway" torque required to get the engine components rotating from standstill, and the second is the ability to keep the whole lot "Motoring" at sufficient rpm 'till the engine fires.
The first requires pure torque, the second is a function of horsepower.
Your question seems to ask for decent motoring rpm, so either starter, assuming the are of similar Hp/Kw rating will perform accordingly. The engine when motoring merely acts as a brake (dyno) on the starter, so it follows if they have similar ratings, they will crank the same rpm. I doubt if either, on a SBC, will struggle with getting the whole deal up to motoring rpm. If breakaway torque is an issue with your combination then choose the 6.1 geared one.
The factors that determine starter characteristics are a lot more involved than most would credit, but the simple answer in most cases is to overrate, as most modern geared starters do.
A greater influence on choice would however be intended application. I havn't pulled up the CSR site, but generally the 3.75 geared starters are based on the older wound field types, and the 6.1 geared ones are PMGR. The "rougher" the service conditons (track type etc), the better to go wound field. Don't let anyone tell you otherwise, PMGR starters are always more fragile, though always lighter.
Again, and in no particular reference to anyones product, try to buy a unit based on an OE (genuine Hitachi/Denso/Mitsu) machine, suitably adapted, if your budget will run to it. A lot of what is out there is "pattern", and like the offshore crank/rod issue, you get what you pay for. And as a rebuilt American brand name rod would be preferred by many over a brand new offshore equivalent, don't turn your nose up at a properly rebuilt OE based starter.
John.
The first is the "Breakaway" torque required to get the engine components rotating from standstill, and the second is the ability to keep the whole lot "Motoring" at sufficient rpm 'till the engine fires.
The first requires pure torque, the second is a function of horsepower.
Your question seems to ask for decent motoring rpm, so either starter, assuming the are of similar Hp/Kw rating will perform accordingly. The engine when motoring merely acts as a brake (dyno) on the starter, so it follows if they have similar ratings, they will crank the same rpm. I doubt if either, on a SBC, will struggle with getting the whole deal up to motoring rpm. If breakaway torque is an issue with your combination then choose the 6.1 geared one.
The factors that determine starter characteristics are a lot more involved than most would credit, but the simple answer in most cases is to overrate, as most modern geared starters do.
A greater influence on choice would however be intended application. I havn't pulled up the CSR site, but generally the 3.75 geared starters are based on the older wound field types, and the 6.1 geared ones are PMGR. The "rougher" the service conditons (track type etc), the better to go wound field. Don't let anyone tell you otherwise, PMGR starters are always more fragile, though always lighter.
Again, and in no particular reference to anyones product, try to buy a unit based on an OE (genuine Hitachi/Denso/Mitsu) machine, suitably adapted, if your budget will run to it. A lot of what is out there is "pattern", and like the offshore crank/rod issue, you get what you pay for. And as a rebuilt American brand name rod would be preferred by many over a brand new offshore equivalent, don't turn your nose up at a properly rebuilt OE based starter.
John.
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bracket boy
Cobra, John
Thanks for your input(s) on the starter. I called CSU about the starter and one of their tech fella's told me the 6:1 ratio would spin it faster. I agree with you on the gearing as it is the same as gearing your car. I had a CVR unit that worked very well and had no complaints at all. Loaned it out and my "friend" sold it.....maybe I should try and get another one of them. It had a Nippendenso motor on it and a starter rebuilder here in town says they are pretty good units.....
Jay
Thanks for your input(s) on the starter. I called CSU about the starter and one of their tech fella's told me the 6:1 ratio would spin it faster. I agree with you on the gearing as it is the same as gearing your car. I had a CVR unit that worked very well and had no complaints at all. Loaned it out and my "friend" sold it.....maybe I should try and get another one of them. It had a Nippendenso motor on it and a starter rebuilder here in town says they are pretty good units.....
Jay