biggest on pump gas

[87lightweight]

hi just picked up a 87 gn project, was wondering whats the biggest turbo i can go and still run 93 octane and what size injectors to go with it? i am planning to use alky injection and go with a front mount ic, the motor is already 30 over, mild cam, ported heads, not much help on tuning where i am located so i want a good dependable setup mostly for the street :wink:

 

[corymc]

what fuel pump do you have?
60# are good no ecm mods needed
i run a 6152 but i think you can run a 6776 dbb
you need a stall converter with most larger turbos also

 

[Dwayne]

.....if you can't close the hood, then it's too big........

 

[jcawley3]

.....if you can't close the hood, then it's too big........

Thats right!:biggrin:

 

[ijames]

With stock heads a 6776 is about the practical limit on pump gas (I run one). Any bigger and you are just giving up more and more spoolup but the heads are such a choke point you won't make hardly any more peak power. With ported irons you could probably run a 70 but I don't know if anything bigger would be faster or not. The alky will help let you run more boost but the 6776 is such fun on the street that I'd still recommend that. You'll need a 3000-3200 stall converter for best 60's (maybe a tad tighter if dbb) with the 6776. 60's are the minimum size if you really want to max out your tune on pump gas - you need bigger injectors running 93 octane than race gas.

 

[callmeebryan]

remember children (and i say this as a 20 yr old :biggrin......

BOOST does not make power. Airflow makes power. This is why in a situation of a 61mm turbo vs a 70mm at the same boost, the 70 will make more power hands down.

That being said. I know a couple guys that are running the 70dbb on pump gas... the 70bb is a mid-9 second capable turbo, and who knows what that has changed to now that the new boosted series of turbos from pte are out!

As far as "the biggest turbo on pump gas".... well the sky is the limit on that one.

For a good street setup, depending on what converter you have, and whether or not you want to change..... i would go with a 67 dbb with 72lb injectors. With dual nozzle alky and a good tune/launch/driver, you could be low 10's with it. On pump gas you could go low 11's.

 

[87lightweight]

i am going to install the walbro pump, and whatever stall is needed also, i guess what i am mostly looking for is setup that i dont have to mess with when i am done (minimum tuning)

 

[Blazer406]

remember children (and i say this as a 20 yr old :biggrin......

BOOST does not make power. Airflow makes power. This is why in a situation of a 61mm turbo vs a 70mm at the same boost, the 70 will make more power hands down.

Unless I was asleep in fluids.... the more pressure thru a given restriction (heads and intake).... the more CFM (airflow)

The only reason the 70 can make more power at the same boost is if the air temp is lower....

Also... there comes a point when you give up too much down low with the larger turbo.... that the smaller turbo will be quicker.... even though the max HP might be higher with the bigger turbo..... you gave up too much spoolup... and low end torque to get there.

 

[ijames]

Unless I was asleep in fluids.... the more pressure thru a given restriction (heads and intake).... the more CFM (airflow)

The only reason the 70 can make more power at the same boost is if the air temp is lower....

But with a smaller turbo the backpressure is generally higher at any given flow so if you look at the pressure difference across the motor it is higher with the bigger turbo so even if the air temp is the same you will get more flow at the same boost, and then the air will be cooler assuming the bigger turbo is more efficient at that boost and flow so you get more power from two sources not just one. [I love long sentences .]

 

[bison]

The 67 GTQ 3 bolt has been to 138mph in a 3500 lb car in Mellissa's car. No doubt its being worked hard but it laid down the numbers. Nothing but 93 and alky. I plan on running at least 140mph at low boost with 93 and alky with my stage 2. Though i wont push the engine much beyond 20-21 psi on 93 and alky. Not worth the risk to me to be trying for any records. The car will be primarily running c16.

 

[bison]

Unless I was asleep in fluids.... the more pressure thru a given restriction (heads and intake).... the more CFM (airflow)

The only time there would be an increase in cfm is if the pressure was venting to atmospheric and measured on the atmospheric side or on the compressor inlet. Air flow is limited by engine displacement and speed. Pressure has nothing to do with it. Flowing 480 cfm at .5 inches of vacuum or at 40psig is still 480 cfm. Though it will be at a much higher bmep in the cylinder with the 40 psi scenario:biggrin: .

 

[bison]

Another thing worth mentioning is that most of the power is lost on the exhaust side with the 3 bolt housing in high boost applications. This can be verified by checking the pressure between the engine and turbo. It is very high in a 3 bolt setup that goes 135+mph.

 

[bison]

But with a smaller turbo the backpressure is generally higher at any given flow so if you look at the pressure difference across the motor it is higher with the bigger turbo so even if the air temp is the same you will get more flow at the same boost, and then the air will be cooler assuming the bigger turbo is more efficient at that boost and flow so you get more power from two sources not just one. [I love long sentences .]

This is only true if the the compressor is spun on the right side of the surge limit. There is no point in running a 70mm compressor on a 231ci that revs to 5500 and pressurized to 20 psi. The compressor is way out of its efficiency range in that example. Any increase in the exhaust flow will increase the power at any given manifold pressure regardless of compressor size.

 

[callmeebryan]

Bison you are right on the money buddy :biggrin:

 

[Blazer406]

Unless I was asleep in fluids.... the more pressure thru a given restriction (heads and intake).... the more CFM (airflow)

I mis-stated.. slightly. Yes the cubic feet per minute is the same.... whether it at 20 psi... or vacuum.... 1 cu ft of air is 1 cu ft of air......

Fortunately fuel is burned by mass.... and so is air..... and the actual mass of the air (mass per cu ft).... is much higher at higher boost than at a lower boost..... example .... lets say at 0 boost.... your engine could theoretically take in (231 ci) .26736 cu ft in one revolution (for one cylinder)..... mass of air at 1000 ft altitude is approx. .072 # / cu ft. Therefore if you live at 1000 ft elevation... in one stroke that one cylinder took in .01925 pounds of air. Standard atmospheric pressure (0 boost) is approx 14.7 psia (absolute) which is 0 psig (gauge)..... therefore at 14.7 psig... you have doubled the pressure... hence... that same .26736 cu ft of air now weighs (theoretically) ..0385 # (double the weight). With this doubling of air.... you can increase the fuel to burn this higher air mass and theoretically double the engines HP.... this is where the power comes from.

Without writing a book in this post.... the original statement by callmebryan was that boost doesn't make power. It does.... and the more boost you put on the intake the more power potential you have.... because every stroke sucking in more actual pounds of air....


Obviously the effiency of the compressor is dependant on the amount of pressure on the turbine it takes for a given pressure out.... and the spped the wheel is turning...

Keeping it simple... more boost is more air (mass) and can make more power.... period.

 

[87lightweight]

you guys forgot about me, i just had a simple question now i am lost i just want a simple and trustworthy setup for pump gas, i love the help but did not want it to get out of hand.

 

[jcawley3]

you guys forgot about me, i just had a simple question now i am lost i just want a simple and trustworthy setup for pump gas, i love the help but did not want it to get out of hand.

yup....this happens sometime.....

my dog is bigger than your dog!

 

[87lightweight]

for now i was thinking for the money either a ta49 or te62 and unsure on injectors for 93

 

[callmeebryan]

I mis-stated.. slightly. Yes the cubic feet per minute is the same.... whether it at 20 psi... or vacuum.... 1 cu ft of air is 1 cu ft of air......

Fortunately fuel is burned by mass.... and so is air..... and the actual mass of the air (mass per cu ft).... is much higher at higher boost than at a lower boost..... example .... lets say at 0 boost.... your engine could theoretically take in (231 ci) .26736 cu ft in one revolution (for one cylinder)..... mass of air at 1000 ft altitude is approx. .072 # / cu ft. Therefore if you live at 1000 ft elevation... in one stroke that one cylinder took in .01925 pounds of air. Standard atmospheric pressure (0 boost) is approx 14.7 psia (absolute) which is 0 psig (gauge)..... therefore at 14.7 psig... you have doubled the pressure... hence... that same .26736 cu ft of air now weighs (theoretically) ..0385 # (double the weight). With this doubling of air.... you can increase the fuel to burn this higher air mass and theoretically double the engines HP.... this is where the power comes from.

Without writing a book in this post.... the original statement by callmebryan was that boost doesn't make power. It does.... and the more boost you put on the intake the more power potential you have.... because every stroke sucking in more actual pounds of air....


Obviously the effiency of the compressor is dependant on the amount of pressure on the turbine it takes for a given pressure out.... and the spped the wheel is turning...

Keeping it simple... more boost is more air (mass) and can make more power.... period.

Your theory is right.... im not disagreeing with what you are saying....

However you are missing the point. Engines do not make power because of pressure. Your turbo is a volumetric efficiency ENHANCER, FLOWING tons of air into the motor.

Its not exactly true to say "more boost=more power". Sure, if you increase boost, your car may make power... but why? Because its flowing more air, not because there is more pressure.

 

[callmeebryan]

for now i was thinking for the money either a ta49 or te62 and unsure on injectors for 93

I have been itching to sell my barely used t-63e...... less than 800 miles and looks like perfect shape. Its a GREAT street turbo. 6 total passes at the track with it. My car went high 10's on 93 and alky with a 1.59 60'. Ill even sell you my 55lb injectors (same miledge as turbo) that were only at 79% duty cycle during the run.

Ill sell it to you if you are interested. Let me know.

And sorry for the thread hijacking here. But we cant help it, we all love our Turbo Buicks