Discokid

iTrader: (1)

Great power comes with great responsiblity. Where o where have I heard that line, lol.

Hey man, in any car, the more power you have the more its gonna need to be fixed, that goes for the vette too. You gotta be prepared to fix it if you wanna run alot of power. Unfortunately you are gonna find more of devotion than reliability in our corner of the automobile universe. It aint simple as bolting on parts, (not puttin down your intelligence). Like Aaron said, you are gonna need alot of $$$$$, and tuning.

saftysizrs

i know it takes more then just bolting parts on and driving thats why i posted to try to get a little more info i want to make big boost like 30 psi so i can run considerably less for daily driving and such. i dont expect to drive around at full power but i do want to have a it when i want it. i need to be able to drive it around town and down the highway without it falling apart on me but that would not have as much power considering the low boost i would run. thanks for the sugestions arron and if theres any way to do some math to figure out what does what that would be good too

Aaron Cake

iTrader: (1)

BOOST PRESSURE IS IRREVELANT! Stop talking in terms of boost pressure because it means nothing. AIRFLOW is what matters.

The fact that you keep talking about a specific boost pressure (what's magical about 30 PSI?) means that you don't have any experience with turbochargers and you should not be jumping in with both feet to build a 500HP RX-7.

DrunkenBowler

Well stated....

Most of us single turbo owners do not even come close to the mystical "30 psi" and we have 400, 500, and 600 hp rx-7's.... Right now, my setup gives me 462 rwhp @ 18 psi. So, I could jump the 500 rwhp mark if I had it tuned for like 22 or 23 psi...

*shakes head* Haha...30 psi...must be a "cute" turbo

zinx

iTrader: (3)

You guys all sound like a bunch of vaginas.

DjTriXs

This guy may/may not know what he's talking about but in a way, we all get some info/education reading threads like this...

keep up the good work guys, while this padawan learns the rotary master ways.... ;P

Discokid

iTrader: (1)

He probally doesnt think the term cfm sounds cool

scotty305

iTrader: (2)

Aaron Cake, I agree completely with what you're saying, but maybe this will help the original poster...


When you say "boost" you are referring to the number that your boost (pressure) gauge or your MAP sensor is telling you. A motor that doesn't flow well will require a lot of "boost" to make a certain amount of power. A motor that does flow well will make the same amount of power with less "boost."

Power is pretty much directly related to airflow, and the more restrictive motor will require a lot more pressure to push the same amount of air through it. An oversimplified example would be a little coffee-straw compared to the big straws you get from fast food places: you need to blow really hard (lot of pressure) to get the same amount of air to flow through the restrictive coffee-straw compared to the big straw from McDonalds.

That is why a lot of experienced people will tell you that boost pressure is irrelevant, because nobody with half a brain is going to try to make 500hp with a stock motor with coffee-straw ports.

-s-

saftysizrs

i know boost presure isnt nessarly power but i want crazy boost presure so i dont have to run around the city ******* my motor over cause it makes too much power. if i can make the 500hp at 30psi of boost then il be happy at the track but then when im on the street i could run say 10 psi of boost and still have a streetable car. i dont know if this makes sence to anyone. i know i can make way more power way easer and probably way cheaper by doing it your way arron but with the v8's i work on we make power with nos so we can still drive them without rebilding the motor every other week cause the air it need to make power isnt there untill i hit that button. so if i make all my power but having tons of boost presure then i turn it down and then i dont have a monster motor to rebuild every othere week

andresj

iTrader: (8)

ok i think what he is trying to say is that he wants a turbo capable of boosting a lot with reliability when its at low psi?? i'm freaking lost i'm just trying to help out. i'm a newb i just started reading up on this section of the forum cause i'm looking into a turbo myself.

TweakGames

iTrader: (3)

I love it. Please don't get an rx7.

KhanArtisT

iTrader: (2)

They guy stated that he would LOWER boost with a boost controller. I am curious as to why people are even bothering to post in this thread.

Aaron Cake

iTrader: (1)

You're still very, very confused.

I've read this 5 times and can't make any sense of it. You want high boost pressure so your engine will be reliable? Generally the effect is opposite. Higher boost pressure generally equals a hotter intake charge and more stress on the engine. At the tail end of what a compressor is capable of efficiency also drops dramatically.

30 PSI is an ungodly high number and you'll be running a small turbo to make 500HP at 30 PSI. You'll need to run something other then pump gas and you'll be waiting forever for the turbo to spool up to 30 PSI. Few people outside of professional drag racing push those numbers into a rotary (or piston) engine.

Why not go with a large compressor which will be efficient with far less boost? As I mentioned, the GT4088R will make those numbers around 20 PSI. That's a far more reasonable pressure and you're on the edge of what can be done reliably with pump gas. Then when you aren't feeling insane, set the boost controller to 10 PSI and make ~300 RWHP.

Or go with the 4094. Having a larger compressor it's going to be more efficient at higher airflows and will probably make 500HP at 16-18 PSI without the intake heating.

The GT42 is a very capable turbo but it's massive in size. I've seen it put down just over 400 wheel HP at 7 (yes, 7) PSI. It's a lag machine on anything but a bridgeport and it's size makes installation a bit hard.

It doesn't.

The opposite is true. If you intend to run 30 PSI, you'll be rebuilding every week.

I think you need to stop and pick up some good information on turbo systems before go any further. Head to the library and pick up a book called "Maximum Boost". Also get "Street Turbocharging" (the 2nd edition will be out soon). Read, read, and read some more. Stop taking advice from the V8 guys. Generally they are turbo ignorant.

diabolical1

iTrader: (3)

you'll probably take this the wrong way ... and it's your prerogative. that's fine, but i really don't mean it as harshly as it may sound. so here goes ...

just forget about all you know and all you THINK you know. act like you're a 5-year old learning something new, because age aside, that's what you are. doesn't really matter how much you know about V8s and nitrous oxide. very little of that **** applies here.

listen to Aaron. he knows what he's talking about. don't take my word for it, just do a search with his name ...

my humble advice would be to start by learning about the motor itself. learning the basics like combustion phases and port configurations is critical to any and everything you're going to spend money doing. when you finish learning the basics, then get yourself familiar with fuel and ignition requirements for rotaries. look at sample curves and/or datalogs. they are out there.

500 HP for the street is possible, but you may simply find it completely unnecessary after driving at 400 or even 300+. my point is don't try building Rome in a day. you're not yet ready for it. you've already stated that you have no support readily available to you:
also, these are reliable engines, failures are mostly due to greedy, cheap, dumb and/or neglectful owners. choose your parts wisely when you build. if you're serious about 500 HP this will be especially true for you (block, porting, wastegate configuration, etc.)

none of your posts convince me that you're ready to tackle building this car to the level you want yet. the fabrication skills you've alluded to are irrelevant because the car is not going to tune itself and there's a world of difference between a 500 HP T2 and 500 HP-cabable T2!

finally, read up on turbocharging. again, start with the basics. like Aaron Cake, i'm curious as to why you keep referring to 30 PSI. what's with that? choose your power goal and find a turbo that will achieve it based on your port-type and the turbo's efficiency map. also look again at what boost controllers and wastegates do.

get familiar with the basics here. most of that stuff can be found right here on this board. it will take time obviously, but no one's going to spoonfeed that stuff to you. when you read and have more specific questions, i'm sure people will be more than willing to help. some people get pissy when they're told to read because of the time it takes, but always remember that everyone's time is precious to them.

for the record, i'm willing to help you. PM or e-mail works, the worst that i'll say is "i don't know."

good luck if you're serious about this.

1

EDIT:
apparently Aaron was posting as i typed this novela, so consider it reinforcement instead of advice.

saftysizrs

ok thanks for all your help everyone, i know i got my work cut out for me when i try to build this but i do know to go slow once i start tuning it. if there is (and im sure ther is) any formulas to get thing like the turbo effenicy maps and how much fuel and what size ports figured out before i do the work to it id love to have them. i know you dont seem to understand what im trying to say about the 30 psi so il try one more time and if it dont make sence then **** it iv got lots of info to work with but here goes. i want to run 500hp at 30 psi, i will have a boostcontroller to get said pressuer. this will be for the trace and will be hard on the car but i dont race every week so im not worried. i will have a 10 pound spring in my wastgate so when im on the street i will shut off my boostcontroller and only run the 10 psi so that i have way less hp and am less hard on the motor. again if you dont get what im trying to say then forget about it if i makes sence to you then let me know. and dont worrie about me rushing into anything i will take my time and do all the recherch i can on everything i can do. thanks again for the help.

TweakGames

iTrader: (3)

Insanity: doing the same thing over and over again, expecting different results. I think I'm going to boost 30 psi tomorrow, this guy makes it sound fun.

bcty

hahaha why even bother guys this guys clueless. You want to run 30psi? Go get a talon or an evo and dont even look at rx7's. Why would you even want to run 30psi? this 500rwhp mark is easy to attain with the right turbo at a lower boost. You would just be super heating your air and puting way more stress on the engine. Why dont you try reading a bit and maybe goto howstuffworks.com and actually learn something.

Aaron Cake

iTrader: (1)

I'm going to give this one final attempt.

Expressing thanks by taking advice and learning from it is far more effective then just saying "thanks".

There are compressor and maps available for almost all turbos. I say "almost" because some of the brand name turbos (HKS, etc.) are bastardized/customized versions of standard OEM (Garrett, Holset, etc.) turbos and the manufacturers can be tight lipped about maps. The best you can do in this case is find a similar turbo by measuring the wheels. So if you head over to the turbo manufacturer's website you will find maps for each of their turbos. Look at the map of the turbo you are considering and compare it with the airflow of your engine. From there you can get a very good idea of how much power the thing will make at what RPM and efficiency.

Search the forum for "stock port CFM", "street port CFM", etc. to get an idea of how much flow to expect. For stock ports, 300 CFM is a good start. Then convert that to pounds as most compressor/turbine maps express it in weight. Of course CFM varies per RPM.

It doesn't make sense because it's stupid. There, I've said it. What you are trying to do is *** backwards and totally useless. It shows a complete lack of understanding on the basics of how this stuff works. I don't know if I can put it more bluntly then that.

WHY, WHY, WHY 30 PSI? What is so special about 30 PSI that you want to make 500HP at that pressure? Wouldn't you rather make 500HP at a more manageable 20 PSI? Or slightly below 20 PSI? Do you realize that a 500HP engine pushing 30 PSI is going to be a major handful to drive? Power will come on suddenly and explosively as the turbo reaches 30 PSI (assuming you have chosen a compressor that gets it's efficiency in that area...) and before you know it you'll be in the rhubarb wondering what happened.

What I'm trying to say here is that boost pressure numbers are arbitrary and shooting for a particular boots level is not how to do things.

An example would be my car vs. a stock turbo TII. The TII with the HT-18 puts down about 250HP to the wheels on a good day at around 13 PSI. My car with it's GT4088R put down 392HP to the wheels at 13 PSI last time I ran it on the dyno (and since then I've tweaked the map a bit vastly improving the midrange and making a bit more peak HP...my guess is 420 HP to the wheels at 13 PSI). WAIT, WHAT? HOW COULD THIS BE? BOTH CARS RUN 13 PSI!!!!one!!1 It's called airflow. A bigger compressor will push more air into an engine at an equivalent boost pressure then a smaller will. Also it will be more efficient in doing so. Intake temps on a stock TII at around 13 PSI are damn near 140F. Mine? Ambient.

That is a completely reasonable thing to do. In fact, many of us already do it. I run a 0.9 bar spring which naturally makes 13 PSI. I plan to fit a boost controller to not only improve turbo response at 13 PSI, but also allow me to run higher pressures (I would like high 400s to the wheel, or to just break 500) when I feel like it. Honestly though I'm dragging my *** with the boost controller because 400 to the wheels in a 2600 LBs 2nd gen is terrifyingly fast.

However, what is not reasonable is to say that you want to make 500HP at 30 PSI. That's a lot of boost, you will have real problems keeping the engine together. There is no reason to push that much boost to make 500HP. It can be done at 20 PSI with a reasonable turbo.

zinx

iTrader: (3)

You should be running 30 psi with that GT42

zinx

iTrader: (3)

There is a common misconception that a bigger turbo at x psi pushes a ton more air than a smaller turbo at x psi. All things equal, they will may the same amount of power. The reason the bigger turbo usually makes more power is because it is more efficient at moving the air. It only moves more air because the air its moving is more dense (colder).

Discokid

iTrader: (1)

"Harry, my car topped out at 140... I need NOS... this one, and you know what, make that two... and Harrym,... I need it by tonite."

Sounds like that 30psi is for the new Fast and the Furious movie, lol

He is hell bent on what someone who dont know about rotaries and turbocharging has told him. I dont know what Im wasting my time for posting here tryin to help someone who doesnt wanna be helped.

You are a good person Aaron, despite his ignorance, you try to still help this kid. Why did he post a question here if doesnt want to learn.

Dudemaaanownsanrx7

iTrader: (23)

First off, if you find a turbo that is efficient @30 psi you will be making alot more then 500 hp.
If you only want 500 HP at such a ridiculous boost level as 30psi then that same turbo will also make 500 hp at 20 psi. WHY? because it will be so far out of its efficiency range that it will be making more hot air then power. So the whole thing would be pointless.
All you would be doing is running more boost just to say you're running more boost. And you're motor will almost certainly pop the very first time you hit 30 psi. So it doesnt matter if you only plan to run 30 psi when you race, the first time you do it your engine will be toast from detonation caused by 250 degree intake temps. So please get that 30 psi number out of your head!

Also a 10 lb wastgate spring will not control 30 psi of boost. you will need at least a 15 psi spring for 30 psi.

if you want 500 hp then you will need something like 720/1680 cc injector setup

As already said no one here that wants their engine to last runs 30 psi!

So if you really want 500 hp then get $15k, a gt 40 or gt42 run 20-22 psi, get a meth kit, a 10lb spring 720/1680 injectors,top feed fuel rails, big fuel pump, fuel pressure regulator, get the engine ported, ignition amp, #10 plugs, big intercooler, engine management, at least a 3" exhaust straight through, a clutch/pressure plate that will hold the power.

Once you've done all that save your money some more and replace all the parts that break.

cptpain

iTrader: (1)

you pick a turbo by its efficiency rating in % at a given cfm over a given rpm the turbo spins at. this will give you the "ideal" psi the turbo is efficient at making its most effective power. period.

there MANY turbos that can make 500hp without pushing 30psi which as everyone has said, is an ungodly amount of boost from any turbo.

you want an all around car right?

the best "bang for buck" turbo that i think everyone can agree with is a GT35R. makes great power, capable of 500hp on certain a/r and trim size, and can do this with 20+psi and you can still make a little over 300hp on "low" boost.


like everyone has said. do not think of boost pressure, it is only a "guide number"

30psi on an LSx motor is VERY DIFFERENT from 30psi in a rotary which reacts very well to turbocharging. which is why, the more you read, people make over 300 even 400hp on as low as 12-13psi on a specific turbo.


learn about turbos, and learn how to read compressor maps FIRST before you pick a turbo.

fc3snari

j

kenn_chan

whoever this is really has no clue, when he cannot differentiate between airflow and a magic boost number, and thinks he can turn boost down with a boost controller he has not done any research and honestly does not know. Kudos to AAron Cake for being extremely patient. Now the mods just need to lock this

kenn

Edit: yes you can turn down boost with a boost controller, but no lower than your spring pressure allows, which he has not considerd.