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Discussion Starter #1 (Edited)
I want to know what kind of power "single" turbo is capable of making running on pump gas, in my situation, 91octan CA shitty gas.

to my knowledge, PSI produced by a single turbo is same as PSI produced by stock twin, with the exception single turbo produces boost more efficiently while stock twin over heats=less efficent=less power output.


so on pump gas, single turbos cant run too much boost because it would still knock and detonate, then it is very possible for a 470rwhp BPU runing 100 octan to beat single turbo...say a T78/full fuel/electronic running 91octan.
this raises the question of advantages of running a single turbo when high octan fuel is not as accessible. if one uses his single turbo supra as daily commute and runs into a NOS'd SS, he would be in trouble.

I'm not trying to put down single turbo, I personally love how big single sounds and feels, however, I just want to hear the other side of story.

thanx guys!

Jonas
 

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Oh, my poor mis guided friend! With over 2400 posts, come on you should know this!!

all else equal MOST all single turbos will produce more rwhp at the same psi as the stock twins.

-You see at 17psi a large single or big twins will be flowing MUCH more air than the stock twins are...thus, you engine is making more power.

Example: my T76 @ 17psi = 507.7rwhp on 93 octane...go fine me a stock twin car w/o nitrous making that much @ 17psi...why? Because my T76 is flowing alot of air at 17psi.

Additionally, the stock twins are getting out of their efficiency range around 18psi or so...where as big single are just Starting to get into their efficiency range.

I'm sure you'll get a ton of replies.....


Jay
 
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Discussion Starter #3 (Edited)
Jay,

I did mention how bad stock twin is at same boost compare to single turbos, but I just didnt know how much difference.
now that you gave me a #, its much easier for me to compare.

my main concern of this post is power output of single turbo on pump gas and low boost that wont be able to run race fuel all day long...
 

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If you are willing to use a big turbo (T88) and 272 cams with extended rev limiter you could keep cylinder pressure low (torque) by using moderate boost but through good volumetric efficiency hold the resulting moderate torque to high RPM, thus making good power.

For example, lets say 91 octane on a T88 will let you make 450 ft-lbs (rear wheel) of torque at 6500 rpm. That would get you ~557 rwhp.

I bet you could make ~600 rwhp on 91 octane. But not on a small, quick spooling turbo that creates high cylinder pressures at moderate RPM.
 

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Isn't it amazing when you see people on this forum for so long and still come off as a newbie??? It's time to post less and read more...LOL

Philly Single said:
Oh, my poor mis guided friend! With over 2400 posts, come on you should know this!!

Jay
 
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Discussion Starter #6
lets not pick on my knoweldge of single turbos. I'm actually posting for a friend of mine.
I did remember Bruce Nomura telling me about how bigger turbo pushes more air and efficiency related issues. like I said, I'm looking for #'s of single turbo on pump gas/low boost (cuz high boost on pump gas is not smart). and when single run low boost, it looks like its very vulnerable. read my post, and help by reply what I ask.
MADMKIV, I see you've made a smart choice by adding a link to put you on ignore list. good for you.
:bthumb:
please behave and dont trash this thread for me.
thanx
 
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Discussion Starter #7
Lagtime said:
If you are willing to use a big turbo (T88) and 272 cams with extended rev limiter you could keep cylinder pressure low (torque) by using moderate boost but through good volumetric efficiency hold the resulting moderate torque to high RPM, thus making good power.

For example, lets say 91 octane on a T88 will let you make 450 ft-lbs (rear wheel) of torque at 6500 rpm. That would get you ~557 rwhp.

I bet you could make ~600 rwhp on 91 octane. But not on a small, quick spooling turbo that creates high cylinder pressures at moderate RPM.
to be specific, I'm refering to T78 turbo kit. with stock internal, full fuel/electronics, 18psi, 91octan, how power is it capable of?
I heard from a DSM guy that 17-18psi on T78 isnt even in the efficency range for its size.

thanx
 
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Discussion Starter #8
Its possible for a fully tuned bPU on race gas to beat an untuned single on 91oct. A untuned t78 would have a lot of lag. It would run pig rich and you wouldnt be able to safely turn up the boost with the shitty gas without your egt skyrocketing.

Right now I'm waiting for the aem ecu to come out if it ever does so I can take it to the dyno and have it tuned. I am running 1.2bar right now on crappy 91oct and by the seat of my pants I know im making less than 450rwtq. You definitely have a chance against a untuned single. You would have a hard time keeping up with a fully tuned single even on the 91
 

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Thanks Jonas for posting this for me.

We have a friend that installed a T78, Greddy 3-rows, VPC,GCC. He's got stock everything else. I went with him to get his car dynoed last week. We didn't have enough time to get the race gas, so we went ahead and dynoed the car with 91 octane (the highest shitty gas we can get).
At the last several runs, he dynoed at 455 rwhp and his a/f is at 10:1. The guy that dynoed his car told us we shouldn't boost any higher (17psi) because of the shitty gas we're using and if we turned up the boost higher the car will start to detonate. So , he doesn't want to continue with the dyno.

So has anyone in California dynoed their car with the shitty 91 octane gas? I'm pretty sure not everyone runs race gas every day.
 

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10:1 is way to rich... he needs to lean it out to make some more power, and since he went with a T-78 he might as well get some 264/264 cams so he can atleast get close to 500RWHP on 91 safely

supra178 said:

At the last several runs, he dynoed at 455 rwhp and his a/f is at 10:1. The
 

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MADMKIV said:
10:1 is way to rich... he needs to lean it out to make some more power, and since he went with a T-78 he might as well get some 264/264 cams so he can atleast get close to 500RWHP on 91 safely

My friend was hitting 11:1 at 5100~6000, and after 6000 it's 10:1.
then the shock came---455 rwhp
 
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Discussion Starter #14
I didnt know he was running that rich, that could also be a reason why he felt sputtering. he did just put in fresh NGK3330 correct?
I guess he would rather see a pig rich dyno chart then a "blowers" chart like Hank..."A/F 18:1", I guess its natural that all these T78 guys thinking obout blowing engine every minutes. its gonna be hard for him to turn that knob and start leaning out fuel curve. even at BPU+ I dont have the gut to lean my fuel out:eek:
 

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Few BPU cars can put down much over 400 rwhp on pump gas.

Most single turbo cars put down 500-550 on pump gas with stock cams. With upgraded cams, as Chip and Peter mentioned, more HP can be had at the same boost level by moving the torque curve to the right. I believe people with 272s put down about 600rwhp, with Jesus doing 700 with an intake manifold, ported head and more boost than normal (21 psi).

My datalogger reports over 16% more airflow than it ever did BPU, at the same boost level. I've got a T66, cast manifold and the stock MAF.
 

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I don't know how much of a difference from 91 and 93 octane. That shitty 91 octane is the highest available on pump gas.
Basiclly, has anyone with single turbo tried to dyno with 91 octane gas and with stock internal?
If everyone in California with a single dynoed at about 450~475 on pumped gas then I personally don't think a single turbo is a good buy.
Let me explain, my friend already spend 11,000 for his turbo kit, fmic, vpc, gcc,fuel system. He did the installation himself. So he saved some $$ for the labor. If he wants to run about 500~600 HP then he needs to get some 100 octane. Our 100 octane costs $4.10. It just don't add up.
That's why I really have doubts about going single. If on pumped gas can produce 550hp then it'll be a different story. My BPU dynoed at 420rwhp. If I had paid 11,000 and only gets 455 on 91 octane, I'll kill myself. That's why I'm wondering what's everyone else getting on 91 octane. Thanks in advance!!!
 

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Zerosoul said:
I want to know what kind of power "single" turbo is capable of making running on pump gas, in my situation, 91octan CA shitty gas.

to my knowledge, PSI produced by a single turbo is same as PSI produced by stock twin, with the exception single turbo produces boost more efficiently while stock twin over heats=less efficent=less power output.

Jonas
The PSI question, one I get from every ricer at every gathering "how many PSIs are you boosting?", is not comparable between turbos. The best analogy of this is a real life example. Think of a coctail straw/coffee stirrer. If you were to blow down this tube with a preassure in the straw of 20PSI, the amount of air moved as a volume could be measured. Compare this to blowing down a garden hose at 20PSI or even 10PSI and I think you can make the comparison. "Boost" or preassure built up inside the engine is actually a better measure of the inefficiency of the engine to be able to flow the air. Stock twins moving 18PSI, of very hot inefficient air, can not really be compared to an efficient, cooler single turbo moving a higher volume of air at the same boost level. This is the theory anyway, not just the heat of the stockers, it is also the volume moved.
 

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Hmm, after reading that many posts with answers that are half correct, I'm shocked. I think what people mean to say about "more air" is that the larger turbos give dense air. The larger turbo will make the same boost at cooler temps thus giving denser air (which means more power). It's not that you're physically moving more air but you're giving "better" air to the engine.

Another one is about 17 PSI being out of the efficiency range for a T78. Maybe on a 20 liter engine. You can't go by flat out PSI because you don't even know what RPM or displacement the engine is. That Mitsu's 2.0L or our 3.0L isn't going to make that T78 hurt making 17PSI unless we start revving to some very high RPMs.
[edit: It's about how much air flow it takes to create manifold pressure. If you have more space to fill, that turbo has to move more air. This is why a larger engine or higher rpms will make it tougher on the turbo to produce the same PSI level]

Lastly, I truly think a single turbo CAN lose to a tuned BPU on the street. I would like to take this from my own experience. Before I get into the general details let me say that most Single turbo owners end up working little bugs here and there in their systems than i've seen with BPU cars until they replace everything with reliable high end hardware. Anyhow, to my point on this subject.

Most single turbo guys are running some type of fuel system that is adjusted for a single boost setting for a nice A/F plot. Many of these folks have tuned for race gas and high boost. When we end up lowering boost because we're not using race fuel, we start running VERY rich. This can mean a big power loss at the same boost. I'm sure this power loss varies but for some of us running super rich this can totally kill power.
 
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Discussion Starter #19
supra178 said:
Let me explain, my friend already spend 11,000 for his turbo kit, fmic, vpc, gcc,fuel system. He did the installation himself. So he saved some $$ for the labor. If he wants to run about 500~600 HP then he needs to get some 100 octane. Our 100 octane costs $4.10. It just don't add up.
Oh man...it costs that much to go single?! i guess i havent done enough research, ive always thought it cost less than 10K to do a good singe setup. it seems that our 91 really kills you guys :( as regards to your friend, he should be able to lean it out a lil bit and see more gains..but then again i dont know where your "sweet spot" a/f ratio is. right now i run 13:1 and the car loves it..no ping/detonation at all, and come nitrous time i can lower it down maybe to 12.5 and still be fine :) heres an idea sherman....DONT EVER GO SINGLE :D hehe, so that way i wont feel like im goin reverse whenever we race
 
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Discussion Starter #20
Silvino, there are a few things that contribute to power with turbos.

1) Intake air temperature. This is what you talked about.

2) Amount of air being moved. Contrary to what you said, large turbos do in fact move more air than small turbos. This is the largest reason that they make more power than smaller turbos.

3) Backpressure. Large turbines and large exhaust piping with minimal bends yield less backpressure than their smaller counterparts.

You can't just say that it's the "cooler" air factor that yields the power since power is a function of these three variables (among MANY others).

Sean
 
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