porkyzilla

iTrader: (1)

ok guys...well on a pretty stock l98 how much boost should i run with no modifications, and with fuel pump, and computer tuning what kind of boost can these motors take stock

i will be running twin 14b's tdo5hybrid's, so what kind of boost can these motors take

CrazyHawaiian

My 91Z28 has been boosting 6psi for 55k miles on the stock L98. Blower went on at 75k miles. I change my oil every 2000 miles. hahahah

ChrisFormula355

He's referring to turbos, which is entirely different than a weak 6 psi from a centrifugal blower. 6 psi from a properly sized turbo is a hell of a lot more power to be punishing the motor with.






I'm running 10 psi on a stock mustang block and I wouldn't think twice about doing the same on an L98 as long as the right tune is there and you don't do something silly like run stock timing/gas.

KS91Z28

What? 6 psi is 6 psi of boost np matter where it comes from.

88 350 tpi formula

iTrader: (9)

turbo's don't draw as much hp to make the 6hp but, I find it hard to think just because it is a turbo the 6 psi it's super special.

just that the proper turbo setup at 6psi can spool very quick so you can keep the 6 psi through a much longer rpm band

ChrisFormula355

That truely shows your lack of knowledge then. All boost is not created equal. For every 200 HP a centrifugal blower makes, it takes 100HP to drive the pulley. Turbos are free spinning.

porkyzilla

iTrader: (1)

thats why in top fuel drag turbo's are band because of efficency,

and i forgot to mention i will be runing a very quick spooling turbo's 14b's twin so i wont have any problems spooling fast..

KS91Z28

No, no, no, no. We weren't talking about how much HP it takes to spin a blower vs a turbo. He was asking how much boost a stock L98 could handle safely. Get it straight before you start talking about my lack of knowledge. 6 psi from a turbo is no better than 6 psi from a blower. Boost is boost. Granted, how it is created is a whole nother story, which is what you're trying to argue.

CrazyHawaiian

Nah hes just all pissy because his friend owes me money and he cant seem to keep out of our business. The guy asked how much a stock L98 could handle, and I gave him my experiences of boosting my stock head/block L98. 6psi for 55k miles on a L98 = safe. What else needs to be said? Do you think anyone really needs you to tell us how much boost you run on your mustang, or insinuate that my blower is weak because I happen to own it? You need to seperate your personal agenda from the tech forums. Boost is boost. If anything, the blower requiring power to make power would be HARDER on his engine compared to a turbo. I would think twice about running 10psi on a stock L98, these motors dont come with strong internals. I would say you're pushing it (would definately work, but might blow it up). As for fuel and tuning, you have some options. You could use a mechanical FMU with a secondary inline pump (Vortechs way of doing it) combined with the right ignition that can pull timing per lb of boost (to prevent detonation). Or you could use a 749 ECM and an aftermarket fuel pump (my way of doing it). You could also go standalone ECM (very expensive). I'm sure there are other solutions I haven't listed here. Lets leave it up to Chris to tell us what he uses on his mustang.

porkyzilla

iTrader: (1)

to a certain degree...a blower is usally alot harder on a motor for the simple fact that torque is right there, and a turbo takes time to spool up expecially from a drag launch, lets put it this way
first picture a stick stuck in the ground and your trying to bend the stick to the ground without breaking it, with a blower its like hitting a baseball bat agaisnt the stick dead on so it snaps thats why the bottom end or drivetrain breaks more on blower/nitrous motors,

Now using the same anaylogy a turbo is like putting the bat against the stick and bending it.

but thats not what im asking, im trying to ask how much boost the stock bottom end or valvetrain can take given the proper fuel to air ratio

ChrisFormula355

HAHAHAAAH I'm sorry, did YOU just say that?? Re-read your entire post then think for a second.



And I was giving technical data pertaining to the original thread starter, he is planning on doing twin turbos, not a single SC.

TraviZ

iTrader: (2)

will the ecm know to retard the engine under boost?

83 Crossfire TA

iTrader: (2)

Please explain to the rest of us how 6psi from a blower is different then 6psi from a turbo as far as the engine is concerned?

Ah, forget it, you won’t because it isn’t.

First, a turbo IS a centrifugal supercharger, it is powered by a turbine (thus the name turbo) rather then a belt/gears.

Boost is boost, assuming similar adiabatic efficiencies (both a centrifugal blower and turbo are capable of similar adiabatic efficiencies, both are in the >70% range when they’re well matched to the engine), in other words, at the same temperature, 6 psi from any source will be the same density ratio which will determine how much fuel you can mix and how much power the engine will make.

[I need one of those game show buzzers that they play when someone gives the wrong answer]

This is sorta like comparing apples to watermelons. Most of the ford HO engines got forged pistons and REALY CRAPPY heads. Later engines got hypereutectic pistons.

Either piston is much stronger then the stock cast pistons used in 3rd gen f-bodies. Heads that flow less result in a smaller increase in flow with the same density ratio of air under boost, which means a smaller rise in BMEP and less of a tendency to break things.

That being said, the answer to the question depends on your definition of “how much can they take,” how good the tuning is, are you running race gas…? No matter what, you will be detonation limited, not limited by how much HP the bottom end will tolerate, but of course, as the amount and how often you push that amount through the bottom end increases the length of time it will live before needing a rebuild will get shorter.

I plan on experimenting with where the real limit is with some boost, race gas and maybe even a little spray later this year, but I suspect that I’ll never _really_ find the limit. I expect things will let go whenever something ends up not quite right and I get some detonation.

KS91Z28

Good analogy (sp?), but that is more like comparing a roots style blower to a turbo. A centrifugul supercharger would act more like the turbo in your comparrison.

Either way, 83 Crossfire TA is right. You're going to be limited by detonation issues before you have to start worrying about the strength of the bottom end.

porkyzilla

iTrader: (1)

well instead of all this ramble can anyone answer my question any experience i really dont care where the boost came from as long as its boost

i will be running a prominator, adj fuel pressure regulator, and msd with boost timing controller

anondude13

Don't turbos tend to have higher IAT's than superchargers because it is blowing air right by an exhaust turbine?

83 Crossfire TA

iTrader: (2)

I’ve answered your question… nutshell, whatever you can tune to control detonation. It’s really up to your tuning.

No. There is no direct contact and the air spends so little time in the compressor housing that any heat conducted into it is marginal compared to what it pics up from being compressed.

anondude13

Just thought I'd throw that out there. I'm from fairfax, if you want to meet up sometime let me know.

daverr

iTrader: (1)

same can be said about turbos. For every 200 hp turbos makes, it takes 100 hp to drive it.

ChrisFormula355

How is that so?? Turbos are exhaust driven, and having installed twin turbo on my mustang after driving it on the street for a year without turbos I can gaurantee you that I did not lose 100HP off boost, in fact it feels nearly identical when I'm not in boost.

I did post this thread on turbomustangs.com and they informed me that 6 psi IS 6 psi, however there is still some confusion because the example was given that the volume of air could be much more.

Example:

6 psi from a T-76 versus 6 psi from a SN89 Paxton entry level blower....obviously different power outputs.....agreed?? This is where I'm confused as to "boost is boost."

83 Crossfire TA

iTrader: (2)

Off boost you’re not using any energy to spin the turbo since it’s not spooled.

On the same engine, 6psi from a t76 will be the same as 6psi from an SN blower assuming that the airflow is in a range where both compressors are at the same adiabatic efficiency.

nightrider87

ah i know what your issue is exactly

Boost is just a measurement of the pressure in this flowing system.

So if you have a really poorly flowing setup, and you want to push lets say 700cfm of air through it, the boost levels you'll need to move that much air are going to be high.

Take a really good flowing engine, push 700cfm through it and your boost levels will be a lot lower...less restriction.

teh difference between a big turbo and an entry level blower is this...

the paxton might only be able to move a maximum of 600 cfm of air. Put that on a lawn mower engine and it'll produce tons of boost, put that on a well flowing 350 and it might actually be a restriction. All turbos/supercharges hit a maximum amount of air that they can move its just wehre that level is that separates your two examples. (the 600 is a more or less arbitrary number. i don't really know what it flows)

the big turbo can move a lot more air and doens't hit the upper limit that that blower did.

However, if you put the blower on a badly flowing 350 and set it to 6psi, you'll make about the same peak power as a the turbo, set at the same boost pressure, on that engine.

howver, you could turn the boost up on the turbo and make a lot more power, where as its going to be hard to pull much more power out of the engine with that supercharger.

Dustin Mustangs

iTrader: (1)

Hmmm...this one maybe??

Do this forum and everyone that uses it a favor and stop pretending to be even the least bit knowledgeable on this subject.

anondude13

Maybe because it takes at least 50 more horsepower to drive a supercharger than a turbocharger...

83 Crossfire TA

iTrader: (2)

No, actually the power use is very similar... I posted some numbers in that turbomustangs thread.

CrazyHawaiian

See I thought the original question was how much boost could the motor handle before blowing up, not which one (turbo/super) will make more power. I gave my experience, but Mark there provided the best answer and he is 100% correct. It would all depend on how well you can prevent detonation.

Steven89Iroc

Wow, lots of 'interesting' discussion going on here.

I agree with Mark, it's all about the efficiency (heat generated).

I'm getting tired of always using my Talon as an example in my posts, but it's what I have boosted at the moment and have had lots of experience with, and the theory is the same. Someday in the not terribly distant future I'll be able to give my Camaro as a twin turbo example.

That being said, My Talon was a lot slower on the stock T25 at 18 psi with the same setup as the T3/T04B at 18 psi. That's because the T25 was really spinning and heating up the air to make 18 psi, whereas the T3/T4 was just getting started. However, at 12 psi (stock T3/T4's external WG spring setting), the two really didn't feel much different aside from spool characteristics and the fact that the T3/T4 still pulled more up top mostly due to the much larger turbine side. That's where the T25 is still plenty efficient, so it makes less of a difference.

On that note, that also makes a difference in turbo's, the turbine backpressure. It's obviously a lot less before a much larger turbine side, that helps flow of course, even with the same amount of intake pressure.

Turbo's in question, in comparison...

Steven89Iroc

From everything I've researched, properly sized turbos do take less overall energy to drive than properly sized centrifugal (for the sake of this discussion) superchargers. In that case, the turbo should theoretically make more power, although it isn't as much of a difference as people would like to believe.
I'll see if I can find that article that was posted on here before...

Here's the turbine side of the two turbos...

Steven89Iroc

OBTW, this argument has been beaten to death. I just have to take the stick and smack that horse! It doesn't seem to be getting to everyone.
Here's the numbers from the article, I don't know more info than that.
Notice the centrifugal made 17 more peak hp, but the turbo made 56 more ft/lbs on the same 9.5 psi. Also notice the turbo's average numbers compared to the supercharger's, that's not even funny.
As usual, it all depends on the rest of the combination, but at least there's a direct comparison on the same setup...

-------------------------Baseline------Centrifugal------Turbo--------Roots
Peak HP------------------392@6000------617@6000---------600@6000-----535@6000
Peak TQ------------------386@5200------561@5200---------617@4200-----513@4600
Min Boost-------------------------------1.7@2500------5.7@2500---------4.8@2500
Max Boost------------------------------9.5@6000------9.5@5100---------8.0@6000
Ave HP(2500-6000rpm)-----310-------------412------------460---------394
Ave TQ(2500-6000rpm)-----365-------------494------------564---------483
Ave HP(4000-6000rpm)-----352-------------518------------555---------472
Ave TQ(4000-6000rpm)-----371-------------542------------585---------497

TQ@2500----------------------------------360------------490---------440
TQ@3000------------------340-------------405------------500---------450
TQ@3500------------------355-------------450------------560---------475
TQ@4000------------------365-------------500------------610---------500
TQ@4500------------------380-------------525------------610---------505
TQ@5000------------------375-------------555------------600---------505
TQ@5500------------------355-------------555------------560---------485
TQ@6000------------------354-------------540------------530---------475

HP@2500----------------------------------170------------235---------210
HP@3000------------------190-------------235------------290---------250
HP@3500------------------240-------------300------------375---------325
HP@4000------------------275-------------375------------455---------375
HP@4500------------------325-------------450------------525---------445
HP@5000------------------360-------------525------------575---------485
HP@5500------------------380-------------575------------600---------510
HP@6000------------------395-------------617------------600---------535

ChrisFormula355

Just how is it that I'm pretending to be an expert on the subject when in FACT the reason I even posted this on turbomustangs.com was to GATHER INFORMATION??

I just don't understand the attitude from some people on this website. (hence the comment "arguing with some idiots").

porkyzilla

iTrader: (1)

ok guys last time im getting ticked off my thread keeps getting hijacked I DONT CARE WHICH IS MORE EFFIECENT ill be running two 14b turbos off of 1st gen eclipse

does nyone have any experience with boost on a stock l98 what it took to prevent detonation, what stock motor can take in boost, the steps you have to take for higher boost i want to start out with 10 and work my way upto 15lbs of boost

KS91Z28

Porkyzilla, 83 Crossfire TA has been trying to tell you that there is no definate answer, but since you want an actual number, according to a graph I found on ATI's website, you could probably get away with 5 or 6 psi non-intercooled, or 9 psi intercooled.

Steven89Iroc

Kenton (89JYTurbo) has run as much as 7 psi intercooled AFAIK on his stock '89 L98 with the smaller Thunderbird T3's.

You won't get away with a lot of boost efficiently with two 14B's on a 350 anyway. At least plan on a good intercooler setup and/or water/alky injection.

TraviZ

iTrader: (2)

what i think hes getting at is, you cant just say that, preventing detonation, you can run 50psi of boost on that stock motor. even without detonation you know that motor would blow.

83 Crossfire TA

iTrader: (2)

It can actually happen the other way around, where the larger turbo is in a lower efficiency island then the higher one if the turbo is too big for the application (but it’s actually difficult to do without hitting surge and causing other problems)



actually, with some of the better supercharger designs you’d be surprised. You’ll find that their power use numbers are getting much closer to the actual amount of power you need to move the volume of air that they’re moving at the pressure that they’re moving it (ie, there isn’t much room for losses).

Never thought that article was too fair. Somebody with a little creativity could have picked a test that would have shown any type that they wanted winning. That being said, as long as you’re not getting into the range of the serious, dedicated drag engine, it’s much easier to pick a turbo that matches sufficiently well to give good results over a broad range.

83 Crossfire TA

iTrader: (2)

huh, if you wanted to run it on straight toluline...

CrazyHawaiian

For my setup I'm using the MSD ignition that retards timing per pound of boost (select 1 through 3 degrees), thats pretty much the only detonation control I have. My 6psi is non-intercooled and I always run 92 octane gas. I'd guess that the stock L98 could handle a little more boost with this same setup I have. I cant increment boost per pound, my current tuning setup is really lame, and I dont have the right sensors to monitor for detonation, so I wouldnt even try.

I'd say everyone else is on par with answering your question. Set the turbos to low boost first, then work it up little by little by adjusting the wastegate until you find the limit (detonation). Things that you can do to prevent detonation, high octane gas, worst case 92 from the pump, even better 76 cool blue (100 octace) or even better then that straight up C16 race gas (117 octane). Definately get an intercooler. Think about different types of injection, some people use straight up water, alchohol, methanol, or more ofthen than not, mixtures of water and one or the other (alky or meth). Some people even spray nitrous on the intercooler to cool the air charge. Devices that retard timing also can really help, you could use a MSD box like I do, or even some ECM's or standalone EFI ECM's can do this through the ECM. And I would do everything possible to monitor the situation while finding that limit, definately a knock sensor, WB02, and even EGT sensor can help warn you of detonation. I wanted to give you my experiences so you know whats safe, but I'll be the first to agree 6psi is a little conservative, and definately not the maximum.

CrazyHawaiian

Well your first post in this thread didnt have much to do with gathering any information. And then posting it on another forum and refering to us as idiots because we didnt automatically agree with you, that wasnt very nice. Not very MATURE. I think the attitude you got was totally normal. Then again, I am a PSYCHO PATH, so take it for what its worth. And next time, please try not to change the subject. The thread was supposed to be about the boost limitations of a stock L98 motor, not which type of FI is "better." Thanks.

Dustin Mustangs

iTrader: (1)

BTW, you gave your know-it-all answer to his question before you even posted this on tm. I just don't like to see people misleading others with their ignorance.

ChrisFormula355

Here's some boost advice:

Yall can blow me

Guido

Here is some advice, you can shut the hell up