I want to know how much mph I will gain in the 1/4 mile with a d1sc at 5psi? My mods are Lt's/ory, 3" cutout, LS6 intake, ported tb, and a 224r cam. What mph gain can I expect runnning 5psi on a d1sc with FMIC? What is the normal mph per lb of boost?

 

I would try more boost car will sluggish in lower rpm's 7-9 psi you will be ok

 

Oh it will eventually see about 8-9psi when tranny is built, but right now I'm running a stock 4l60e that isn't going to like anything more than 5psi and might not like 5psi. Right now I'm looking to see low boost at low rpm. Like 5psi at 6000rpm

 

nobody has any input?

 

I would say about 12-14mph depending on the tune up.

 

its funny you say that , how did you know , mine doesn't seem like it has any power down low running somewhere between 4-6 lbs

 

i would guess 5 psi is 8 mph in 1/8 so 12 or so in 1/4 but it really depends on convertor.

 

Damn really? 12mph on 5psi? That's more than I was looking to gain lol.

 

i am thinking it will gain 30-35% more power @ 5 psi so about 10 mph in the 1/4 is my uneducated guess. down low it will still be sluggish because it won't be making very little boost untill the revs start climbing.

 

I'll guess 7 in the 1/4.

 

Well, since noone asked, I will. What did your car run before this? Big difference if your car ran a 13.3@108mph and you add 5psi of boost vs. if it ran a 11.5@117 and now add 5psi to it.

Fact is, there's no clear cut, exact answer that anyone can give you. Get the car built, get it to the track and start to sort things out. You have to figure out how much extra traction you're going to need, how much stall, what rear gears, what rpm to launch at, what rpm to shift at. All those things are going to impact your times and trap speed (trap speed to lesser extent) and need to be sorted out at the track.

 

It isn't building boost yet until the rpm's get up

 

Car ran 12.2@113 spinning with a 1.98 60ft. I think it would do 11.8@114 with tires. And I forgot to add it has a circle d 3400 stall and 3.23 gears

 

I'd be happy with 7mph at 5psi. I plan to shift it at low rpm. Like 6100 rpm.

 

Why would you shift it at a low rpm? Chances are, it's going to make peak hp at 6500-6800. 600-700rpm doesn't sound like much, but once you go into the next gear, it's going to be lower in the rpm band, which will be lower torque and hp, and will yeild slower times and lower trap speeds.

Think of it this way. At 6100 rpm, your car will make lets say 500hp, but at 6800 it makes 530hp. you're leaving 30+ hp on the table by shifting it at the lower rpm.

It goes back to what I said that you'll need to play with shift points and launch rpms as well as tire pressure etc etc to maximize your times. If you were only cutting 1.9 60' times spinning, it's going to be worse with the extra power from the procharger.

 

Oh I now where my engine makes best power and all about shift extension... I don't think your understanding what I'm trying to do.. If I get decent gain on 5-6psi shifting in lower rpm than I'll be happy because that's exactly what I'm trying to do. That way I can get it all set up on a lower boost level and than when I get tranny built I can up rpm to 6600 rpm and make 8lbs of boost at my motors peak power range. Right now the goal is to get it setup while keeping the stock 4l60e for a little while.

 

Honestly, with as much as you're already spinning, and you plan to shift at 6,000, I don't see your mph going up more than 2-3mph. If your trans is shot now, it's going to be even worse with more power going through it.

 

What? I never said the trans is shot. It's never had a problem in the 25,000 miles I've put on it. 4l60e's don't like high rpm. Just trying to get it to last awhile longer.

 

It's very hard to say what gains you will see with just 5 psi, because very few around here have ever gone with such a low boost setting. The blower will be spinning much slower than one that is set up build 7 to 8 psi of boost, that it won't start making boost until a much higher rpm. Because of the cost involved with tunes, pulleys and blower belts, I would initially get it set up to make 8 psi of boost, then short shift it until you get the transmission built. That way you'll have more usable boost lower in the rpm range, and it will keep cost down. You will still end up having to have the tune touched up for the new transmission and converter, but overall you'll still save money. the hardest thing on these automatics is to go wide open throttle when the car is in overdrive. Manually dropping it into 3rd before going wot will enable the transmission to last much longer. Bob

 

This was kinda what I was talking about doing only I worded it a bit differently. I'll set it up at my peak rpm to be at 8psi and than bassicly have it tuned so it shifts much lower so I'll see less boost/rpm so the transmission will last. I have free tunes for this car so going back for tunes isn't to big of a deal. BTW I very rarely go WOT in OD. If I ever race I hold it in gear.