intercooling is the key to pump gas

quote 95 GSXracer:
Intercooling is the absolute KEY to pump gas power. If anyone is interested in this concept, I can elaborate further.

by all means please do, and could you also give a quick explain to fuel- cut? i'm not sure but i think i'm hitting it...

You would know if you were hitting fuel cut...

...its like running into a brick wall.

I agree with Kevin's statement, that by lowering the charge air temp, you are going to produce more power. Colder, denser air equals more power.

i wanted to know why intercooling is the key to pump gas. i'm not that new...

and as far as the fuel-cut, i want to know the parameters it kicks in at, or if i could be hitting boost cut.
my problem could be that i'm boosting too much too quickly (punching it in 3rd around 3500 rpm)[causing fuel-cut?], or that my air filter is bouncing around too much from violent accel and sucction forces, thus not giving laminar airflow at the MAS [boost cut?]...
when i'm on it hard in 3rd sometimes it kicks hard, almost like a backfire, boost will blow a little and hold, but a big kick, like ouch!! it doesn't do it all the time, if i accelerate smooth but quick, it will be ok, but when i get on it hard wether it be highway or street, it will kick a couple seconds after i hit full boost [16.5 lbs]. so my best thinking is what i stated above. or if there are any other ideas?????

i wanted to know why intercooling is the key to pump gas. i'm not that new...

and as far as the fuel-cut, i want to know the parameters it kicks in at, or if i could be hitting boost cut.
my problem could be that i'm boosting too much too quickly (punching it in 3rd around 3500 rpm)[causing fuel-cut?], or that my air filter is bouncing around too much from violent accel and sucction forces, thus not giving laminar airflow at the MAS [boost cut?]...
when i'm on it hard in 3rd sometimes it kicks hard, almost like a backfire, boost will blow a little and hold, but a big kick, like ouch!! it doesn't do it all the time, if i accelerate smooth but quick, it will be ok, but when i get on it hard wether it be highway or street, it will kick a couple seconds after i hit full boost [16.5 lbs]. so my best thinking is what i stated above. or if there are any other ideas?????

I just wanted to second this question, I have the exact same symptoms and I wanted to make sure it was fuel cut.

the reason intercooling is the key to pump gas is because intercooling as we all know reduces charge air temp. The problem with running pump gas is that a turbo will heat up the air enough so that when it comes in contact with wour fuel charge it will ignite the fuel causing pre-deationation. intercooling will reduce these temps. The more the intercooler can lower the charge air temps, the more boost you can run. Another key to pump gas in alcohol injection. alcohol has certian properities to is that make it real well suited for a turbo car. 1. It cools as it evaporitates, 2 alcohol is real octane rich, 3 alcohol is a anti-deatoniate. look into it. I run 24 psi on pump gas with stock intercooler and iron heads. It must be able to do somethign for you 2.0 guys as well.

Thats right. The single biggest reason why intercooling is key, is knock. The extra power you get from denser air is always good, but its less of an issue for us. Turbocharging pressurizes the air, which automatically increases the density, even if some is given back up to heat. (PV=nRT for you still in physics class, the Ideal Gas Law is helpful to illustrate all this). But the single biggest factor in how much power you make is how much air you can flow safely. To move more air on a given setup, i.e. displacement (fixed at 2.0 unless you stroke it), head/intake flow capacity, etc, you need more boost. More boos tis more heat. More heat is more knock. More knock is turning the boost back down. There is the limit. Intercooling is the countermeasure to all this. For me the difference between knocking at 17 psi on pump gas, and getting up to 25 psi before knock (with MUCH more airflow) was intercooling. Pump gas power also requires a TON of fuel as well. For example, my FIC 850s are nearly maxed out at 95% duty cycles. On race gas when you run a good deal leaner, you have a smaller fuel requirement. This is how I ran 12s on the stock 450s, race gas.

Another very important thing to note is that intercooler efficiency is FAR more significant than compressor efficiency. If anyone is interested, I can run through some math with you guys and we can compare the difference between the two, and see exactly why IC efficiency is so much more important.

Fuel cut is determined by airflow. When the ECU see the airflow value, it compares it to a limit in one of the tables in its program. If the numer is less than the limit, nothing happens. If its greater, the fel cut sequence starts. It does just what the name implies, cuts fuel. This is why it feels like you hit a brick wall. Its not a stutter, not a stumble. Just BAM, no power. Then it comes back. Typically, if you have it you know it. ;)

i wanted to know why intercooling is the key to pump gas. i'm not that new...

and as far as the fuel-cut, i want to know the parameters it kicks in at, or if i could be hitting boost cut.
my problem could be that i'm boosting too much too quickly (punching it in 3rd around 3500 rpm)[causing fuel-cut?], or that my air filter is bouncing around too much from violent accel and sucction forces, thus not giving laminar airflow at the MAS [boost cut?]...
when i'm on it hard in 3rd sometimes it kicks hard, almost like a backfire, boost will blow a little and hold, but a big kick, like ouch!! it doesn't do it all the time, if i accelerate smooth but quick, it will be ok, but when i get on it hard wether it be highway or street, it will kick a couple seconds after i hit full boost [16.5 lbs]. so my best thinking is what i stated above. or if there are any other ideas?????

Same thing is happening to me. If i accelerate smoothly and firmly there is no problem, but if I try to floor it the car studders really bad.

A stutter is different from a brick wall. Check intake leaks, plugs, wires...the basics.

ok, here's the deal, i just installed the GReddy type-24 intercooler, and this just started happening. so being the genious that i am i used advanced psychic problem solving and after determining that all the evidence stacked on the tires was inadmissable, i reluctantly decided it must be the new intercooler, and something needs to be adjusted. [running a profec b spec 2] i could boost 18 psi on the old intercooler, with no problems, but now [i understand that the t-25 is smoking crack to keep up boost in the newly lenghtend pipes, and because of this loses boost early because of an inability to hold the wastegate] i'm only throwing 16psi, at the most [because of this problem (and i know that 95 says that 16 is optimum for the t-25)], and i guess it really is like hitting a brick wall, it just slams me during a mass accel, at full [16psi] boost, passing thru 5k rpm... i just dont want to be worried about florring it and getting slammed and my turbo falling off [because that's the kind of thing that comes to mind when i get kicked]...

just another quick thought, i got about 90k mi on it, could this be a timing problem? i started modding the car 6 months ago, it had 79k on it. might i need a new timing belt job?

You guys might want to check your valve springs. The sputtering could be valve float. weak springs will do that to any engine. espically tubo cars

Stock DSM springs are good to 8500 rpm. I dont think anyone here is going that high, and I have never seen one go bad. But thats an interesting point, I didnt know that.

Everyone should be putting no more than 60k miles on a tbelt. It wont cuase any of these problems though. The timing belt is either good, dead, or skipped a few teeth. Either way youd know if something was wrong. One tooth off and the car wont run correctly. With 90k on the belt, I would change it imediately. Also, its important to note that you can make 10000 HP and it wont affect the tbelt. Reving it high will though. The higher you rev the motor, the more frequently the belt should be changed.

Just an added note. Valve float will happen on a perfectly good spring under some conditions. All valve springs have a frequency that if matched by the engines vibrations or motion of the camshaft will cause a valve to float. Only way around it is to use a double spring setup.

sort of an update... i softened my BOV [i had tightened it way down when i was venting it, now it's dumped again] and i think that might have fixed it [different mas reading?]... a friend told me about the HKS FCD? any thoughts?

a friend told me about the HKS FCD? any thoughts?

Dont bother. If fuel cutis an issue the correct way to solve it is with the right eprom (requires the emprom ECU) like TMO, DSMlink, or that jeff guy's chips. The next best thing is to go to larger injectors and use an AFC or similar to comepenate, which will put off fuel cut by an airflow amount proportional to the increase in injector size. Those FCD type things cant work well on DSMs, anything you do to make it htink you are flowing less air will lean it out. ;)

I don't know if this is relevant to fuel cut, but I just had a crushed 1 gen bov installed on my 97 gst (only other mods are cat back, KN cone filter, and hacked dumped tube). I decided to try and vent the bov as uposed to recirculate it cause I heard you can get lucky with dsm s sometimes and it will still run properly. The only problem I notice is in first gear whenever I get to 4000rpms, it vents all my boost! note: this only happens in first gear! I'm planning on throwing the pipe back on to recirculate but I just wanted to know why it was venting all my boost!

Probably has to do with the reduced load the motor sees in first gear. Either way, even a crushed 1g BOV will leak too much to run vented. Unless it is "Gus-modded." Too much work. Just dump it back in. :)

You guys might want to check out this website. It's a GN dedicated site, but a turbo's a turbo.

http://www.gnttype.org/techarea/turbo/intercooler.html

ok... so i feel as if i'm up against the "Tuning wall" right now, and i just need to progress my engine further to make it work better.. thanks for all the info, as usual, much appreciated...

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Originally Posted by BoostedSpyder
i wanted to know why intercooling is the key to pump gas. i'm not that new...

and as far as the fuel-cut, i want to know the parameters it kicks in at, or if i could be hitting boost cut.
my problem could be that i'm boosting too much too quickly (punching it in 3rd around 3500 rpm)[causing fuel-cut?], or that my air filter is bouncing around too much from violent accel and sucction forces, thus not giving laminar airflow at the MAS [boost cut?]...
when i'm on it hard in 3rd sometimes it kicks hard, almost like a backfire, boost will blow a little and hold, but a big kick, like ouch!! it doesn't do it all the time, if i accelerate smooth but quick, it will be ok, but when i get on it hard wether it be highway or street, it will kick a couple seconds after i hit full boost [16.5 lbs]. so my best thinking is what i stated above. or if there are any other ideas?????
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I was having this same problem before. I was told that it was something wrong in the fuel system. I replaced everything through it and still wasnt fixed. Then I was told to change my plug wires. So I did that and it fixed the problem completely. :grinno: hope this helps you.