Would no tight up top hurt my performance

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BOP4ever

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Joined
Jul 6, 2007
I was talking to a respected trans guy here today concerning converters for my 87 GN. He told me the PTC 9.5 would be too much for my mild combo and actually probably slow it down in the quarter mile due to the lack of slip up top rpm wise. Just wanted to run it past you guys since id hate to spend more for PTC and go slower compared to his which I read great things about and only slips about 7-11 percent vs the PTC 3-7 estimated from our conversation.

Thanks
 
To be clear he was not downing the PTC at all and said it was great for cars running quicker than 10.5. It was just to tight for my lower hp combination.
After re-reading a past conversation with Dusty he kind of said the same thing, that the 9.5 was more Than I needed for mid 11s and his 10 inch would work as well or better if that was the end game. I just don't want to have to by another later I guess so I am trying to be sure on my choice.
 
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A combo like yours really benefits from a lock up converter to keep the rpms at a range that will make the best use of your available horsepower.

With a stock cam and unported heads your powerband pretty much ends at 5200-5300 rpm and keeping the revs between 4400 and 5200 will give you the best times.

When I ran a similar setup thats how I ran my best times, by locking up the stock converter.... you cant afford to throw away 11% of your available powerband/rpm range and expect to run a good number.

A ptc 9.5 may not be the best choice but one thing for sure is 11% slip in a converter is not going to help you run a good number.

Have you run your car at the track and do you know what slip% your present converter is?
 
Yes it ran 12.55@110 and 12.45@109 shifting to od after the 1/8 mile.
Slip calculators showed 20% plus slip.
 
From what I gather Redneck , art carr, and now freak show are all from the same people.

You want slip. If you lock the converter to early it will drag rpm down to low way out of the power band. When you shift into 2nd you want it to slip 1500-2000rpm but couple to within 900rpm top of 2nd. The higher the rpm the lower the slip percentage will be also. A converter slipping 1000 rpm at 4000 engine rpm = 25% slip. The same 1000rpm converter slip at 6000 engine rpm = 16.6% slip.
 
To clarify, lack of slip doesn't slow a car down. If the converter is to tight and holding the engine in a lower rpm range, that's when it can slow the car down. The 9.5 can be stalled for pretty much any combo. When I say overkill I am saying the 9.5 is a lot of converter for a 11 second car. A $500 converter can get there so it saves some money compared to the $1,000 9.5. In cases where the converter is to tight it's usually where a converter is spec'd for 30 psi but the car is only at 20 for example.

I do have guys who use the 9.5 with a stock cam and run high 10's. They picked up et and mph over other lock up converters.


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what are the goals for the car?after reading the linked thread you stated you wanted 10 more mph over 109/110 mph that you were running if that is the goal you must realize to get that your 44 has to be all in and making as much boost as it can.having run a 10 sec/120+mph 49 car on the stock motor in the past I can tell you its not going to happen with a ton of slip in 3rd gear and the car needs to leave in the high 1.4/low 1.5 range.
 
Mr.Spool said:
what are the goals for the car?after reading the linked thread you stated you wanted 10 more mph over 109/110 mph that you were running if that is the goal you must realize to get that your 44 has to be all in and making as much boost as it can.having run a 10 sec/120+mph 49 car on the stock motor in the past I can tell you its not going to happen with a ton of slip in 3rd gear and the car needs to leave in the high 1.4/low 1.5 range.
Click to expand...
Goal is to fear no new showroom stock to mildly modded car from a dig or for a 30 to 100 roll or so . I think a car that at a min can bust a basement 11 sec et @ about 120 should be good 90 % of the time.
Must cruise and drive nice too.
 
What is your trap rpm when your saying you have 20% slip?

20% slip at 110mph with a 2800 stall is WAAAYYY off as in something in the converter is broke or something else is going on.

Another option is to open, inspect and restall your converter. If it already has front and rear anti-balloon plates and just needs a stall change $200 would likely get you what you need. I restall other converters often.
 
4750 Rpm @ 110 mph
That's in OD with a 275/50/15nitto tire.
5100@91 in third gear.

What's that calculate out to?
Numbers came from turbo link log.
 
I'm getting around 21% in 3rd gear at 91mph. That's calculated with your tire size and 3.42 gears. It seems way off unless there's something crazy going on inside the converter. Does it feel really loose driving around? What's the stall speed at 1psi boost?

Have you compared turbolink to actual trap speed at the track to make sure it's correct?
 
Dusty Bradford said:
I'm getting around 21% in 3rd gear at 91mph. That's calculated with your tire size and 3.42 gears. It seems way off unless there's something crazy going on inside the converter. Does it feel really loose driving around? What's the stall speed at 1psi boost?

Have you compared turbolink to actual trap speed at the track to make sure it's correct?
Click to expand...
I don't have a tach other than the stock bar thing so no. I can say the 5200 shift light turbo tweak ses light comes on right at the 1/8 mile so I think the turbo link is close bases in that fact.

Converter stalls around 2800 at zero using the turbo link data. If you follow the link in the earlier thread it shows stall I was at zero to 2 psi on the brakes .

Car drives and feels good around town no problems moves like stock really no complaints other than I am thinking it is getting over powered down track at wot.
Trans shifts quick and firm etc...
 
Dusty do you know if ptc can restall a old school art carr 9 inch non lock up converter and possibly do upgrades to it ? Or are those converters not worth it ?
 
I've seen some really fast close to stock cars run a 9.5" PTC. If I was looking to run a number with a near stock engine I'd be using the 9.5" PTC without a doubt. Another thing to mention is me or anyone else can't tell you what slip is going to be. The more torque the higher the slip. Stock heads and cam are absolutely done at 4800. It's all the turbo after that. We've gone much faster on a stock converter with much less slip than the times you posted. You shouldn't have to ever be in 4th. Converter is likely broke.


Sent from my iPhone using Tapatalk
 
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434nova said:
Dusty do you know if ptc can restall a old school art carr 9 inch non lock up converter and possibly do upgrades to it ? Or are those converters not worth it ?
Click to expand...

Yes they can be restalled but that depends on what your looking to do with it. Some have sent them in to be tightened but there was no more adjustment in them so I had to swap them to a 9.5. Very few people want them looser. Depending on what stall arrangement it has, I have been able to get some 400 rpm tighter. There's really no way to know without cutting it open and looking at it. Worst case, you would get a core credit towards something that would work for you.
 
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