biggest on pump gas

[GNBRETT]

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.

Im dizzy....:tongue:

 

[87lightweight]

also a couple more newbie questions, were the original 87 gn heads aluminum or cast? and does anybody recommend swapping out the dis system for a distributor?

 

[corymc]

cast heads
i looked into the distributor system and the money can be spent better elsewhere

 

[callmeebryan]

also a couple more newbie questions, were the original 87 gn heads aluminum or cast? and does anybody recommend swapping out the dis system for a distributor?

No need to swap out the DIS system until you are running 8's, but even that can be argued :biggrin:

 

[ijames]

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.

Sorry bout the digression. I run 93 octane pump gas almost exclusively, without alcohol injection, and have spent a lot of time learning to tune right at the edge of detonation. Before I pulled my engine a year ago (I'm a really slow, unmotivated mechanic, sigh ) I ran mid to low 12's for several years. That's at 4060+ lbs going down the track, on Nitto drag radials - drive to the track, let some air out of the tires, and make a pass. My 60' times stunk, mostly 1.9-2.0, because I had some stiff rear springs in the car, so I would run 108-111 mph and 12.1-12.3. Bone stock long block with untouched stock cast iron heads, stock cam, CAS V2 frontmount, 72 lb/hr injectors, ATR headers which hurt spool but make a little more top end power so at a 12.0 are probably equal to but not better than stock headers, 3" THDP, LT1 MAF/translator, 10" 3000 stall Yank converter (don't ask ), and I make my own chips. The usual 160 thermostat and fuel pump upgrades. With a 2.5" ATR downpipe, 40 lb/hr injectors, and TE34 turbo I was out of both turbo and injectors at about 12.70 and 105ish mph. Upgraded to the 72 lb/hr injectors, a PT54 turbo (equal to a TE61 with Precision .63 exhaust housing) and the 3" THDP and got to 12.3-12.4 consistently with a best of 12.01 and a few 12.teens when I got some traction, at 108-109 mph. Went to the 6776 turbo and softer rear springs and got 12.1-12.3 consistently with a best of 11.82, at 110-112 mph. I've run over 111 mph with zero knock retard and zero esc counts for the entire pass - I run at the edge, yes, but don't like to get any detonation at all. Yes, I picked up about .2 or maybe .3 going from the PT54 to the 6776 (these are all plain bearing, not bb turbos), but I really don't think going bigger would gain much since the stock heads are such a flow restriction. Now, with race gas and another 2-7 psi more boost that would be different, but not with 93 octane. You have ported iron heads so I think the 6776 would be a great turbo for you on pump gas or with alky. Yes, you could go bigger, to a 70 or so but the lag gets much worse so I don't think you would like driving it on the street nearly as much. My 6776 spools basically just as fast as the 54 did, and I love it, so that's what I recommend for you.

 

[Blazer406]

Great post Carl.

 

[87NAT]

I agree with the 6776dbb. Keep the combo simple. Throw some air at it with enough fuel(60# inj) and dont detonate.

I run 21 psi with my 6776 compared to 26 psi with ta-60. The 6776 combo is an animal. I dont feel I will ever need to go above that 21 psi mark. I cant hook up at anything under 35 mph on the street right now anyway. Maybe at the track I will add a few psi...

 

[bison]

Back too the original question i would answer with a 6776 or something very similar since its easy to overpower the stock bottom end these days. Though its definitely not the biggest for pump gas. If you plan on running 135+mph then you should consider a GTQ but only after you spent the $ having a reputable machinist throw in a crank kit and girdle or steel caps.

 

[gpadilla1071]

You know, I have been a member for almost a year and it doesn't ceased to amazed me everytime someone comes around with their scientifical answers (e.g. math equations, etc) Anyhow, I love it, because I love learning, but at the same time it's funny how deep some of us can get from a simple question! :biggrin: Thanks guys, all of you are great!

 

[cstavro]

blazer is correct. i'm not just saying that 'cause i'm a mech eng as well

as far as the original poster's question: knock is caused by high temp/pressure beyond gasoline's flash point (dynamic pressure leading to high temp, or inefficient compressor causing too much heat). compressors are rated in lb/min - mass flow.

knock is worst around max bmep, which is max torque. so, just limit boost around 3000-4000 rpm. so you could A) use an electronic boost controller to limit boost in the mid range, and ramp up thereafter, or B) use a really big turbo that comes on after 4000 rpm, or C) just limit boost.

a 61mm will make 15 psi on our motors with an intercooler and no knock on pump gas - more with alky. high 11s to low 12s, 55#/hr injectors. hth

 

[bison]

knock is worst around max bmep, which is max torque. so, just limit boost around 3000-4000 rpm. so you could A) use an electronic boost controller to limit boost in the mid range, and ramp up thereafter, or B) use a really big turbo that comes on after 4000 rpm, or C) just limit boost.

Knock is worse at higher charge temps and high bmep's. Limiting boost would hurt power. Theres a lot more involved in an engines ability to avoid detonation than just bmep. The load and time at load has a huge effect. Add octane, run a slightly fatter a/f, or increase alky flow to suppress knock. Using a really big turbo that comes on over 4000 rpm wont do much for driveabillity unless you run a 4000 stall which would suck on the street.

 

[BetMinesFaster]

+1 on this

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

This will be a good street turbo, I ran a T64e and loved it, not one single complaint, even spooled pretty snappy, came on like a pile of bricks as well, Id say that this would be a very economical turbo and should do what you would like.....

 

[49-blues]

The T-70 i have for sale at $750. shipped.