twin turbos on a manual truck

12valvetater said:
ive only been to this site for about an hour and ive already learned more than i knew other than all the crap flinging it was really useful im in the same boat as this guy with my truck i want something that is going to tow nice and run great but im not looking for a whole lot past 550 at this stage i have the the turbo from dallas turbo sitting in my garage i got it from a friend for 550 bucks it supposedly has a smaller exhaust housing on it and is a 72 mm compressor but i really dont know i havent taken it apart to see would that work alright under my H1C?
Click to expand...

There is plenty of good info on here... and plenty of poo flinging. You'll get used to it. And welcome :Cheer:
 
Forrest Nearing said:
ahh Charles, I see you were running a 7.3... 1.24x the displacement of a 5.9 and I've got to assume the heads flow better than a 12v Cummins because ANY head flows better...

so you had a ball bearing top turbo that moved SLIGHTLY more lbs/min than an S362 on an engine with 1.24x more displacement and it spooled up well? gee, imagine that! :rolleyes:

an S256 or maybe even an S258 map is scaled to an S362 at about 1:1.24... you think that might hit like a freight train on a 12v with a bottom turbo scaled down from your GT47-88 like gee... I don't know an S475?!?!? (a little smaller than that actually) I'm kinda thinkin' it might spool up pretty damn good... you?

go impress yourself somewhere else
Click to expand...


Hey, if you like snappy trucks that fall on their face and lay down up top that's your deal. Has nothing to do with me except for the fact that I might poke fun at you for it.
 
It seems to me to make the best use of power in the narrow power band that we have with these engines. Same reason I dont get people running 3500+ rpm convertors when thats right about where the engines out of steam any way. It makes since to me to utilize the advatanges of the diesel by design....... low speed torque.
 
Charles said:
Hey, if you like snappy trucks that fall on their face and lay down up top that's your deal. Has nothing to do with me except for the fact that I might poke fun at you for it.
Click to expand...

I still don't know where you're getting this BS... there's "snappy trucks that fall on their face up top" and there's drivable trucks with a BROAD powerband, and there's peaky dyno queens (which is what you're suggesting in THIS thread)

I'm sure you can build a 7.3 w/ a broad powerband, but untill you've owned and built a few 12 valves, quit cluttering up threads trying to look smRt talking about **** you aparently don't know anything about
 
stock600 said:
It seems to me to make the best use of power in the narrow power band that we have with these engines. Same reason I dont get people running 3500+ rpm convertors when thats right about where the engines out of steam any way. It makes since to me to utilize the advatanges of the diesel by design....... low speed torque.
Click to expand...

Diesels actually have a pretty wide powerband in comparison to most gassers. Looking at a dyno sheet I have laying on my desk I see at least 500rwhp from ~2500rpm to ~3800rpm. So it made 500+ over a range of 1300rpm. You look at that and intuitively it might seem like a narrow range. But it's actually a change in rpm of 1.52:1. Which is all that matters in terms of Powerband. And is subsequently why a comparably powered diesel will usually outrun a gasser even when the dyno sheets look similar.

For instance, take a gasser that makes at least 500hp from say 5000rpm to 7000rpm. It is clearly making 500hp or more over a range of 2000rpm. That might lead you to believe it has a broader powerband, but that would be incorrect. Because while it makes the power over a range of 2000rpm, the problem is this only represents an rpm change of 1.4:1. Meaning it literally only spun the input shaft 1.4 times faster at 7000rpm as it did at 5000rpm. So truth be told, the diesel above actually has an 8.5% wider powerband than the gasser.

Which explains why a diesel equipped model will almost certainly outrun/outpull a gasser equipped model of comparable power day in and day out.


If that seems off, or doesn't ring true, let me try to explain in another way:

Say you have a situation where you are accelerating the vehicle with each of these two engines one at a time. Say it's from a roll, and at the speed you're starting at each time the output shaft speed of the trans is 2500rpm. Okay, simple enough.

So take the gasser. If we set up a trans where the engine will start the pull at 5000rpm (so it's in it's powerband) it will need a trans ratio of ~2:1. Which is about second gear on a ZF6. We'll just say the ZF6 is exactly 2.0:1 in second since it's actually like 2.1 or so. Alright, so the gasser is in second gear turning 5000rpm with the output shaft spinning 2500 and he nails it. It's making 500+hp and accelerating up to 7000rpm where the output shaft is now spinning 3500rpm. So out of that 2000rpm powerband you got an actual output shaft rpm range of 1000rpm in a real-life scenario.

So take the diesel. Since its powerband starts at 2500rpm it will make the pull in 3rd gear which is 1:1. So it starts at 2500rpm with an output shaft rpm of 2500 and then you nail it and it makes 500hp while accelerating up to 3800rpm where the output shaft is then spinning 3800rpm. Whoa..... the output shaft is turning 300rpm faster even though the engine only accelerated over a range of 1300rpm vs the 2000 for the gasser. Correct.... however, as you see from above, that is a change of 1.52:1 vs 1.40:1 for the gasser.

3800 vs 3500?

Yep, it's the same 8.5% more that we noted above. This is the "magic" behind diesels. And why they actually have a broad powerband even though they don't operate over a broad rpm range. This is because the percentage change to the rpm for a diesel is large.
 
Forrest Nearing said:
I still don't know where you're getting this BS... there's "snappy trucks that fall on their face up top" and there's drivable trucks with a BROAD powerband, and there's peaky dyno queens (which is what you're suggesting in THIS thread)

I'm sure you can build a 7.3 w/ a broad powerband, but untill you've owned and built a few 12 valves, quit cluttering up threads trying to look smRt talking about **** you aparently don't know anything about
Click to expand...


You need to chill.

You're so caught up at this point that you're last few posts look more like an argument as to why a 7.3L engine is a better candidate for a hot street truck than a 5.9L engine rather than anything about turbochargers.

And how does responding in a thread and trying to lay it out straight mean I'm "trying to look smRt" ?

Simmer.
 
In my above example the diesel should have been in 4th gear.... 1:1. Just noticed I typed 3rd for some unknown reason.
 
Charles said:
Don't feel like it.

Melting your brain by actually asking you to use it seems like a better idea.
Click to expand...

All of your posts in this forum are the same. Pointless and annoying. Brain power isn't needed for any of them, just a laxative.
 
why are 70% of powerstroke owners ****ing douche bags?

no one cares what turbos you are running on your 7.3 in the cummins section.

and you are COMPLETELY wrong about a big charger making a truck faster.

my truck with an s300g 57/64/14 @ 40psi was fast as hell. unfortuantly 3rd and 4th gear were tire smoke when the charger lit (16-1700)

as fun as that is, i went to an s400 64/74/.90 @62psi and now shift at 3600 instead of 2700. and the only reason i feel the truck is faster is i have traction because the turbo spools slower and doesnt start to until 22-2400

anyway.... as said

GO AWAY
 
Lucky Jeff said:
All of your posts in this forum are the same. Pointless and annoying. Brain power isn't needed for any of them, just a laxative.
Click to expand...

My initial response to Forrest and most subsequent responses from me were based on the following:

- He was insinuating that for a street truck, smaller turboed, albeit lower-powered, setups are better. Even went so far as to say that they will outrun higher powered setups because the high powered setups are often so laggy. Which is true..... of a botched/ill tuned setup.

- The point I made was that even a moderately sized set of compounds will still light faster than a moderately sized single. As an aside I poked fun at him for choosing insta-spool over power.



My response to the powerband statement was based on the following:

- He stated that diesels have a narrow powerband and that they should be operated as such. Insinuating that we shouldn't be expecting anything but low rpm operation from them.

- My point was that diesels actually have a broad powerband, usually broader than a comparably equipped gasser. Since the thread is about manuals, and powerband has everything to do with shifting, how often you're shifting so on and so forth, I thought it was relevant. I believe I supported my argument just fine.

And I think that sometimes any response longer than a sentence or so immediately shuts off some people's brains. Hence the pipefitter who's got a headache now.
 
Rollin Coal said:
why are 70% of powerstroke owners ****ing douche bags?

no one cares what turbos you are running on your 7.3 in the cummins section.

and you are COMPLETELY wrong about a big charger making a truck faster.

my truck with an s300g 57/64/14 @ 40psi was fast as hell. unfortuantly 3rd and 4th gear were tire smoke when the charger lit (16-1700)

as fun as that is, i went to an s400 64/74/.90 @62psi and now shift at 3600 instead of 2700. and the only reason i feel the truck is faster is i have traction because the turbo spools slower and doesnt start to until 22-2400

anyway.... as said

GO AWAY
Click to expand...


A big charger won't necessarily make a truck faster. But one that's too small DAMN SURE WILL make one slower... especially up top.

Secondly, you did an excellent job showing me what you mean by telling me about how your truck is faster with the bigger charger. I totally see your point, slower trucks are way more fun than fast ones, that's why when it comes to turbos, the smaller the better.

Stick your old charger back on then SA. Or DA as the case may be.
 
JD WOP said:
ahhhhhh I dont get a paragraph
Click to expand...

Well, interland seems to be a popularity contest...

You're apparently only allowed to respond if you get the majority on your side. So I'm going to try and work in as many one liners as possible just to give people the warm and fuzzy and try to minimize factual information and explanation whenever I can.
 
Charles said:
Well, interland seems to be a popularity contest...

You're apparently only allowed to respond if you get the majority on your side. So I'm going to try and work in as many one liners as possible just to give people the warm and fuzzy and try to minimize factual information and explanation whenever I can.
Click to expand...

I kindoff lost you there....but maybe you should keep all this factual info a secret.
 
You must log in or register to reply here.
Back
Top