So after a fresh rebuild done by me with all machine work done by a local machine shop. I decided to go with the wiseco pistons set proper piston to wall clearence and set my sights on 600-650rwhp. Specs on motor are cometic gasket custom, all arp hardware, micropolished crank, all parts balanced, precision intercooler, precision injectors dual walbro, vpc afc, msd dis-4, v-8 b&m oil cooler, koyo radiator, aeromotive fpr, 275 35 18, fresh paint, full titan turbo back, new oil squirters, gonna use the precision 71mm turbo .69ar ex housing. what do you think questions comments welcome
9:1 compression + high boost
- Thread starter quake
- Start date
Don't look at it as 'High boost'
If you are running over 20psi, imho, you have plenty of room to increase the airflow through the engine.
Boost = resistance to flow.
Flow = power.
Let it sink in for a bit
If you are running over 20psi, imho, you have plenty of room to increase the airflow through the engine.
Boost = resistance to flow.
Flow = power.
Let it sink in for a bit
9:1 comp ratio is what I run. Been running for 2 years going on three. But don't listen to me. I run E85 which is basically race fuel anyway
since our engines don't rev as high as a lot of turbo motors, would the engine benefit from the higher compression? Are smaller AR houseings a compliment to higher compression? thanks in advance, I can't decide whether i want to go 9:1 or keep stock compression ratio... also, i don't rmember seeing, Quake, are you running stock rods?
i am running a sp61 with aem and i dont have it completely tuned yet. i have gotten it at 9 psi to 290 rwhp on a dyno dynamic dyno but i have been back to turn up the boost. i have been regularly to 10 psi at 10.5 to 12 a/f and no problems. the timing is a little conservative.
i dont know what your timing will be with that piggy back stuff and running higher boost than 10 psi. the stock ecu will keep the same timing at your higher boost. you may need to set your base timing at 9* or even 8* at first to make sure you dont get any knock.
i also coated my piston tops and chambers to help keep temps down and detonation away. cant wait till i go back to the dyno and turn up the boost and then put in some race gas. i have had some trouble getting the wastegate to go over 9 psi but will have that fixed shortly.
i dont know what your timing will be with that piggy back stuff and running higher boost than 10 psi. the stock ecu will keep the same timing at your higher boost. you may need to set your base timing at 9* or even 8* at first to make sure you dont get any knock.
i also coated my piston tops and chambers to help keep temps down and detonation away. cant wait till i go back to the dyno and turn up the boost and then put in some race gas. i have had some trouble getting the wastegate to go over 9 psi but will have that fixed shortly.
Doward said:Don't look at it as 'High boost'
If you are running over 20psi, imho, you have plenty of room to increase the airflow through the engine.
Boost = resistance to flow.
Flow = power.
Let it sink in for a bit
that's probably the best post i have seen here on SM in a LONG time....if only people would get it....
So what are you advising him to do to take full advantage of this room to make more power? I assume you mean to port out the head and add bigger valves etc. to increase flow........Doward said:Don't look at it as 'High boost'
If you are running over 20psi, imho, you have plenty of room to increase the airflow through the engine.
Boost = resistance to flow.
Flow = power.
Let it sink in for a bit
Can you clearify or dumb down that post so people like myself who arent really "overstanding" what you are saying can make good use of this
Doward said:Don't look at it as 'High boost'
If you are running over 20psi, imho, you have plenty of room to increase the airflow through the engine.
Boost = resistance to flow.
Flow = power.
Let it sink in for a bit
What he means is too many people relate the pressure to the amount of power achieved. Not the case, 18 psi on a stock ct is no where in the same ballpark as 18 psi on gt4067R. Need to think in terms of lbs/min instead of lbs/sq inch
i understand the fact that the bigger turbo will "flow" more air than a smaller turbo at the same psi, but it still doesn't click for me completely. isn't 18 psi, 18 psi? if my piping is holding 18 psi wouldn't that take the exact same amount of air regardless of turbo sizing. i know it isn't this simple, but i was just trying to get this figured out...... in my head, i think 18 pounds per square inch in my intercooler piping is the same amount of air no matter the size of the hairdryer.
gilberjj said:
it IS
the problem is that you are thinking RESITANCE.
That pressure is a resistance to FLOW.
That just means that there is that much resisitance for the amount of flow going from the turbo.
18 psi is not the same amount of air. As a matter of fact it is NOT amount of air. it is the force that is RESISTING the air from moving inside the intake system (ie valve closing, throtlle bottle closing, turbulant air flow in the system etc).
In english
as resistance goes up, flow MUST go down. Regardless if it is 20 lbs/ft^3 or 6000 lbs/ft^3. But if you have 18 lbs/in^2 of resitance against 20lbs/ft^3 or 6000 lbs/ft^3 which one do you think will be affected more (answer the smaller value of the two)
and to borrow what Bernoulli created with his equation
The pressure in a fluid decreases as its velocity increases or said another way.
The pressure in the fluid INCREASES as its velocity DECREASES.
Last edited:
figgie said:But if you have 18 lbs/in^2 of resitance against 20lbs/ft^3 or 6000 lbs/ft^3 which one do you think will be affected more (answer the smaller value of the two)
what do you mean "affected?"
thanks...... i think we are making headway. eventually i will understand this. also, does a t-66 flow more air into an engine at 10 pounds of resistance than my ct-26 would flow at 10 pounds of resistance? this is confusing, because i would think that resistance would be completely up to how well your engine can flow air, not the turbo. ex. bigger valves, and a p&p head will FLOW more than a stock head, so it allows more air to be flowed into the combustion chamber before the valve shuts, therefore the turbo is actually spinning faster to achieve the same 10 pounds of resistance because the engine can now ingest more air....... thats what would make sense to me! i still don't see what the compressor size (or turbo size and capability) has to do with flowing!
is it the fact that the bigger turbine wheel creates less back pressure and allows more air to be flowed into the engine? wow....... im all over the place, but thanks for helping me understand. im trying!!!!
I love you guys.
You've got a lot more factors at play, than just the psi you are seeing on your gauge.
Everything else equal, 10psi from a T66 is going to create more power than 10psi on a CT26, because the 10psi from the T66 is more efficiently compressed. When you compress air, you heat it up. The efficiency of your turbo is a measure of how much more it heats it up than necessary. A CT26 is NOT efficient over about 13psi. It heats up the air to insane temps.
The T66, on the other hand is barely working to compress the air @ 13psi - so your temps are not increasing much over what the Ideal Gas Laws state it should.
Hot air = less dense. Cold air = more dense. The denser the air, the more power you make per volume of air. That's why we run intercoolers, as well.
Now that's just turbo sizing!
Suppose we now take two cars - one a T66 on a log manifold, stock everything else, and run 10psi.
Car #2 has one of Ron's FFIM and tubular header, as well as a set of those 272 cams. Still 10psi.
Car #2 is going to make a little more power than car #1. Possibly in the order of 20-30rwhp, but I would not expect much, at this low volume of airflow.
Now take both cars, and run 20psi. Car #2 is now going to make a LOT more power than Car #1 - why? Airflow. Car #1 is making 20psi, but the air is having to fight its way into the engine, and back out.
Car #2, on the other hand, is having no such problems - the air is easily entering the engine, flowing through it, and leaving the engine. That also means that T66 is being much more efficiently utilized
To specifically answer your questions -
#1) Yes, the T66 is flowing more MASS of air, due to higher density (colder air charge)
#2) The compressor sizing is actually a slightly different part of this equation, due to what I wrote up above - You've got to take into account how dense your air is, and then how well it will flow through the engine. 2 seperate things, working together for more power
#3) The turbine wheel is the exhaust wheel - don't get that confused with the compressor wheel A larger exhaust wheel allows more air to exit the engine, easier.
Turbine sizing is ALWAYS a trade off between maximizing power, and minimizing lag.
You've got a lot more factors at play, than just the psi you are seeing on your gauge.
Everything else equal, 10psi from a T66 is going to create more power than 10psi on a CT26, because the 10psi from the T66 is more efficiently compressed. When you compress air, you heat it up. The efficiency of your turbo is a measure of how much more it heats it up than necessary. A CT26 is NOT efficient over about 13psi. It heats up the air to insane temps.
The T66, on the other hand is barely working to compress the air @ 13psi - so your temps are not increasing much over what the Ideal Gas Laws state it should.
Hot air = less dense. Cold air = more dense. The denser the air, the more power you make per volume of air. That's why we run intercoolers, as well.
Now that's just turbo sizing!
Suppose we now take two cars - one a T66 on a log manifold, stock everything else, and run 10psi.
Car #2 has one of Ron's FFIM and tubular header, as well as a set of those 272 cams. Still 10psi.
Car #2 is going to make a little more power than car #1. Possibly in the order of 20-30rwhp, but I would not expect much, at this low volume of airflow.
Now take both cars, and run 20psi. Car #2 is now going to make a LOT more power than Car #1 - why? Airflow. Car #1 is making 20psi, but the air is having to fight its way into the engine, and back out.
Car #2, on the other hand, is having no such problems - the air is easily entering the engine, flowing through it, and leaving the engine. That also means that T66 is being much more efficiently utilized
To specifically answer your questions -
#1) Yes, the T66 is flowing more MASS of air, due to higher density (colder air charge)
#2) The compressor sizing is actually a slightly different part of this equation, due to what I wrote up above - You've got to take into account how dense your air is, and then how well it will flow through the engine. 2 seperate things, working together for more power
#3) The turbine wheel is the exhaust wheel - don't get that confused with the compressor wheel
A larger exhaust wheel allows more air to exit the engine, easier.Turbine sizing is ALWAYS a trade off between maximizing power, and minimizing lag.