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Discussion Starter · #1 ·
what is about the safest boost i can get with out forged pistons, and still have my car be a good reliable every day driver....
what turbos are best for that and what other mods would i need to support them.. thanks
oh ya how much are we looking
 

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Hellfire Master
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Well there are several required bits of information that would need to be provided in order to best answer your question...

1. How fast do you want to go?
2. How much are you willing to spend?
3. Do you want high boost levels or high horsepower? I assure you there is a difference...

devilmanVISA
 

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Discussion Starter · #3 ·
well i dont care about going a top speed fast.. but i dont want to ruin my engine. and i wnat to be able to drive it every day,
as far as going fast.... i dont know 11's would be cool.. heheh
as far as horse power i dont know.. what ever it will take to get me in that range and still be a safe every day driver..
as for money... i dont know. i dont want to spend a fortune but i am willing for fork out some buck...
like i said i got i got my engine rebuilt.. i got a new transfercase
i got a new clutch. i am going to have my tranny looked at this week well maybe next week... with thanksgiving and all..
i am looking at taking my time to finish it,, its been about 4 months and i can put it together,, but i want do more first......
might as well do it while do it while the engine is out..
 

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Hellfire Master
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Ok here it is then,

If you want to crack 11s, here is a pretty sure fire recipe:

Turbos: several different choices. I will break them down in two categorys
Category1- 13Gs, GT347s, DR500s
This is the first tier of turbos. One step up from stock. More efficient and hold higher boost than stockers. You can run 11s on these but not as easily as you can run 11s on category2 turbos...
Category2- 15Gs, GT357s, DR650s
Second tier of turbos. Much easier to run 11s and have the potential to run 10s with lots of other mods backing them up. More efficient and will hold higher boost than the first tier.
Basically if you are a good driver and have decent support mods you could pull 11s with first tier, but it would be safer to go with second tier. Also you should decide whether you want low, mid, or high 11s as there is a big difference.

Fuel: At least 550cc injectors. Not sure if it can be done with 450s or not, but I guess it is possible. In addition you should drop in a fuel pump to feed the injectors. Several options for fuel pumps but these are generally pretty linear, the more you pay, the more you get unless you are paying for a name, as is the case with the HKS pump...

Electronics: Boost controller. Doesn't have to be electronic, but that is my preference. Stay away from the Apex AVCR as it will occasionally just decide to shit the bed and you will be doing yet another rebuild. Not guaranteed, but its better to be safe than sorry. Fuel controller. Several options here too. If you don't mind some timing retard go for the Apex SAFC or the HKS AFR. If timing retard is an issue or if you ever plan on running bigger than 660 injectorsa get the ARCII or the HKS VPC (you still have to get the SAFC or AFR with the VPC for fine tuning). If you want maximum adjustability and limitless potential get the AEM EMS and RTFM or buy a runer.

Other stuff: Everything else...
Exhaust- downpipe and catback. Gut the precats or get yourself some eliminators.
Free mods- free weight reduction, block off the EGR and remove all of the emissions crap and the throttle body coolant.
Ignition- upgrade this to use a bigger spark plug gap and prevent spark blow out.
Underdrive pulley- liberate your hard earned horsepower.
Driving lessons- you will never pull 11s if you can't get off the line and down the track.

There are other ways to do it as well, but this one is pretty sure fire although I offer no guarantee ;) I suggest if you want more input you do a search as this topic is posted on average of 5 times per week.

devilmanVISA
 

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Discussion Starter · #5 ·
i am sure it is.. thanks for hte infor though..
 

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Discussion Starter · #7 ·
btw what was the apx. cost of that stuff
thanks
 

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Hellfire Master
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One million dollars *places pinky to lips* :D

It could cost anywhere from $5-10,000... but it can be done much, much cheaper than that. The recipe I gave you is for (almost) *guaranteed* 11s and most likely low ones at that. This cost is for virtually every other mod you can do at the level of performance you are at.

I know for a fact that Phalse ran 11s much, much cheaper. Search under his name and see what he had done and how much it cost him.

devilmanVISA
 

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Concerning his first question, though. With stock internals (non-forged pistons, stock rods, and probably a cast crank), how much boost would be safe (no damage to internals)? I ask this too, because I am nearing completion on the mods in my sig and was curious what I could safely turn it up to once the engine is broken in.

Thanks,

Ross
 

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The answer to the question is "how much boost can you run without knock?" What ever that boost level is will be how much boost can you can run with cast pistons. Since that changes from car to car & setup to setup there's no clear answer.

Knock with stock/cast pistons and you'll end up like this:
 

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Discussion Starter · #12 ·
whats about avrage then...
i was hearing or reading that about 15~18 with out forged pistons..
does that sound right.
i cant remember where it was.. may have been horsepower tv.. hard to say for sure though
they said you only need forged pistons anymore if you are running Nitrous, or other additives like that, or an extream amount of high boost
will it make a diffrence if the engine is bored out.. mine is 40 thousanths over...
 

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Average? What are we guessing here? That's no way to do things! Start guessing on the tune with stock pistons and I guarantee you'll go home on a trailer.

You've got a 91 right? You're lucky enough to have a car that can log knock so get a datalogger and find out how much boost your particular car can run safely. Don't listen to anyone that tells you what's "probably safe" because you may be the exception.

See that above piston? I did that at only 15.0psi because I listened to what people thought would "probably be safe." My car is an exception & I can't run as much boost as other people. It doesn't mean I don't make as much or more power...it's just that my timing is so far advanced that I hit knock earlier than most.

Boost alone doesn't always equal power...I bet 60% of the people on this board (pretty much all the loggerless 94+cars with bigger injectors) are down on power because they're running too much boost and the computer is pulling so much timing because of the knock. If they turned the boost down and let the timing make the power they would run better traps while being safer at the same time.
 

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Discussion Starter · #14 ·
so let me get this right.
your saying that if your car is timed better and you have 15 lbs of boost you will run better than a car that is not quit as well timed running 18 lbs of boost
just a guess...
if that is so how do you fine adjust the timeing
 

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Yep...that's what I'm saying. According to my calculations my car makes over 492 crank HP at only 15.3psi on 93 octane & over 522 crank HP at 17.4 psi on 100 octane.

Your base ignition timing can be adjusted with this:
http://www.stealth316.com/2-timingterm.htm
...and a timing light of course.

You shouldn't have to adjust it though. Ignition timing is going to advanced by the stock computer when you run larger injectors and a piggyback fuel computer. Your ignition timing will vary based on your MAF signal which is dependent on how you tune your fuel computer and how large your injectors are. The larger injector and/or the leaner you run the car the lower your MAF frequency will be & the more advanced your timing will be...the further advanced your timing is the less boost you can run safely.

I know it's thick stuff but you need to understand it or else you'll smoke your motor.
 

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Listen to Trevor, he knows his shizzle.

The highest amount of boost you can safely run is dependant on all kinds of things.

First lets define safe.
Safe boost is obviously boost that doesn't destroy your motor. Why does boost destroy your motor? Knock. What is knock? Detonation. What is detonation? Basically it is when your air fuel mixture ignites when it isn't supposed to. This can occur before the plug fires (pre-ignition), or after the plug fires with the left over unburned air/fuel. Knock=BAD.

So what causes knock?
Knock has many different contributing factors. Amount of air in the cylinder. Amount of fuel in the cylinder. Too much of one and not enough of the other and your pistons will look like Bon Jovi's Levis... These are the two big contributors to knock. Another big one is heat. Inadequate quench or poorly cast pistons can cause hotspots on the combustion surface and can cause detonation or pre-ignition.

So lets examine how some of these conditions can occur.
Too much air.
Duh. Turn the boost down.

Not enough fuel.
Duh. Turn the fuel up.

You have to find that happy medium between the two (air/fuel). That is part of the tuning process.

Heat.
This can be caused by more things than I care to explain here. Inadequate intercooling and or inefficient turbos for the boost level you are running are big contributing factors. When air is compressed it is heated. This can be seen by the common equation PV=nRT. If you increase pressure (P) you must also increase temperature (T). The stock turbos could hold pretty high boost levels, but the air will be so hot that the intercoolers will hardly make a difference, your engine will knock, png and then its boom game over. This is the whole reason people upgrade turbos. They are more efficient.

Okay so I have at least partially covered knock and some of its culprits, but what exactly does the engine and the computer do about knock?
The engine is fitted with a knock sensor, which is little more than an overglorified microphone, that is intended to detect the distinct pinging noise that happens whenever your engine knocks. The ECM reads this number and retards the ignition timing accordingly to try and combat the knock. This is something you want to avoid. Pulling timing is bad. It is not good. THat is why yopu can actually have higher horsepower levels at lower boost levels. The air is cooler at lower boost levels and thus less knock-causeable which costs you some air, but saves you some timing.

I realize that is a rather brief and dirty treatise on knock and detonation and if you want more information on it go to www.google.com and search. Take a little bit of time and effort and you will learn more that way. *gets off of soapbox*

Any other questions or any corrections in my logic flow, feel free to post 'em.

devilmanVISA
 

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Even with forged pistons you better avoid Knock. It seems like the stock engine is strong enough to handle a lot of boost as long as knock is avoided. Forged pistons will not help very much but will give you a sloght cushion in avoiding damage.

IMHO, the problem is the factory computer( To much timing with increased boost). once people get the stand alone computers tuned right you are going to see big gains in horsepower with these cars and an increase in reliability......As long as the car is tuned right.
 

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Discussion Starter · #18 ·
so if a stand alone computer is better in your oponion then what ones are recomended.. and which ones are not recomended..
 

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How to tead knock

I have 94 VR-4. What tools I have to buy/install to read the knock?

Thanks
 
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