J Lent

Both. My boost needle starts to move at 1300rpm, but I spool at 1400rpm, by 15-1600 I have 10-20psi & boost goes up fast the harder I push my go pedal. I'd say that it hits 45 psi by 1700-1800rpm empty. I adjusted my wastegate to 45psi because it was hitting 55+lbs. I am not sure how a automatic would act with my setup, but I honestly feel that J-fox is underfueled for the turbo. Look at anyone who complains about spoolup with the 62/71 & they usually have small injectors.

Fishin2Deep4U

I am running a Dodgezilla over a S400 with some M6s, cam, and Edge Juice.

Box on or off, I have no issues spooling the turbos. Temps are not even remotely a concern. I cannot hit 1300 degrees no matter how hard I try.

I tow a light trailer every weekend. 20' jetsled. I get close to 20 mpg at 65-70mph with the box on level 1 and the cruise in use. Unloaded, 23-24 mpg depending on outside temps and humidity. I am at sea level.

I will be making some minor changes to my set in order to get the primary to spool even quicker. But it's pretty fast.

I have a tight auto, 3.54 gears and 285 tires as well.

Dave

Tate

What elevation are you at? I'm around 3500 feet usually, and it does take a bit for this thing to get going.

J Lent

I own a excavating business, we do foundations & utilities, concrete for American Homes out of Morgantown, W.V. & we travel anywhere that we find work through PA., W.V. & Maryland. Elevations are around 2000-4000ft. I believe. I do know that in parts of W.V. I've pulled many hills that say elevation 35-3700ft. Ask anyone from W.V. about route 50 going into Maryland from W.V. It has hills that are 5 miles long at 9-11% grades that are more windy than a snake & tight turns left/right from bottom to top...seriously not one point in the hill where you hold the steering wheel straight. I have pulled 15k# up those hills many times & you are shifting 3rd-4th from bottom to top going in/out of the turbo....no problems at all building 45psi all the way up. Egts never exceed 1300* running sw2, 2x5.

J Lent

That sounds like a good setup that you have there to keep M6's cool. I am not saying that twins aren't great believe me, just saying that the guys running SPS 62 turbos or HTT 62/71/13ss need a injector to spool them....especially with 3.54 gears. I have 4.10 rears.

olddodgetruck

when i had my sps62 i had that turbo on with stock injectors till i got my 150s. it spooled fine with them but it spooled no better with my injectors in. the only difrence was once the turbo was lit it built boost harder and faster. i dont have name brand injectors but scott at mass diesel has to know somthing about injectors because dennis perry ran them. about a week ago hohn had a post about the myth of spoolup with injectors if you havent read it you should. but if you are asking if the sps62 is compareble to twins, there not close. you get everything with the twins.

Muddin_dude06

Well thats why you can spool the charger that much better than everyone else, that makes a huge difference especially since you only have 33's. I have 3.55's and 35" BFG's and my stock charger barely spools that fast, thats with a massive port and polish too! And I agree injectors do not make the spoolup better until boost is already built up past say 5PSI and that is mostly determined by your right foot... I am switching back to stock 215's so I can set my truck back up as a tow rig, I drive oodles of miles and I need mileage not all out HP anymore...

Not trying to pick a fight with you or anything dude but you having 4.10's kind of puts you in a different league when it comes to spoolup IMO...

Fishin2Deep4U

RPM definitely helps things out!

I have always felt that if you are going to use a single, get one that will spool as quickly as possible and get a great wate gate to keep it under control.

Dave

schoust

Rpm is it in a nut shell IMHO. A stick truck keeps the RR's up if you drive normaly,if you drive agressively then all the better in the rpm dept. All I know is My turbo is Awsome if and only if the rpms are up and the thing is begining to spool ,otherwise it takes a little time to get on thye boost for sure. Case in point I was in back of a dump truck at around 28 to 32 Mph and I hit it while starting to pass well I have to say it seemed like an eternity! And there was a lot of smoke! The plus side is once I got it to spool it is unreal and hard to control! The spinning rear tires that is!!LOL! I also believe the the gears and the better flowing head also the available timing boxs are all pluses for the 24 valve and no doubt ,make the sps a good turbo for your truck J.....

J Lent

Do you guys think it makes that much difference from 3.54 to 4.10 gears? Really? I didn't think that the gear difference could give me spoolup 400rpm faster than everyone else is claiming. I thought maybe 100rpm at most.

HOHN

It's a double edged sword. Higher RPM will improve spoolup, but higher load does as well. One would favor the 3.54 gears, the other would favor the 4.10s.

I can rev my truck up in neutral to 2700 and get no boost. I can hold that rpm in 3rd gear and get no boost.

Boost is an indication of engine load as well-- we have to keep that in mind.

Drag racers have known for a long time that turbo engines need taller gears, so while you'll often see the NA guys running 4.56s or something worse, you'll see turbo guys running 3.55s or even 3.07s.

Turbo engines perform best under higher loads.

The caveat to that, though, is that you have to have sufficiently high (numerically) gearing that the engine can get the RPM up to its operating range.

That depends heavily on transmission choice. An auto trans with a loose converter can let the RPM flash up to the operating range we need, so the're very little benefit to a 4.10 ratio over a 3.54. But if you swap in a super-tight converter (think DTT 93%), you'll be wishing for those 4.10s because you won't be able to gain RPM to get your engine into operating range.

With a stick shift, you'll have a creeper gear to help things along, and the difference between the two axle ratios is not significant at launch-- it matters most after you're moving, determining the rpm/road speed balance and hence, the amount of power you'll have at a given speed.

JH

bnold

I tow on a regular basis my twins have NO issues keeping my 6.5s cool... I NEVER have EGT issues... I tow from light to 20k or better..... I believe I the u get what you pay for took me buying 4sets of injectors from 3 different manufacurers before I finally bit the bullet for F1s would have saved so much money in the long run if I would have done it in the first place! go twins and never look back

Fishin2Deep4U

Hohn is right.

The reason why lower gears help the turbo spool at the same speed is mostly due to where in the gear we are adding that load.

In my opinion, the heavier and more bulletproof a turbo is, or one that has the biggest wheel available is not going to spool as fast as a smaller turbo. Just no way around it.

Adding fuel does not help get it lit and sometimes hurts spoolup.

You need heat to get teh charger going. This is why boost drops off close to nothing at cruise and climbs on load, no matter the speed.

Twins can help or hurt depending on what your goals are. Spool with a single is limited to the weight of the assembly vs heat vs rpm.

Dave

muddin_mavric

one obsevation i have made with my 62/71/14 is exactly what hohn is saying. In second gear i cant even break my tires loose with out dumping the clutch of corse. my turbo cant spool fast enough to get more than aboout 20 psi by the time i hit the gov. how ever in third by about 1900 rpm my tires start going up in smoke.

J Lent

Do you get hot with the 4.5 injectors? Any towing?