faq about how much power stock tbi can take
03-11-2008, 07:56 PM
#1
Supreme Member
Thread Starter
iTrader: (4)
Join Date: Aug 2004
Location: southern maryland
Posts: 1,417
Likes: 0
Received 0 Likes
on
0 Posts
Car: 2012 Ram express
Engine: 5.7 hemi
Transmission: auto
Axle/Gears: 3.55
faq about how much power stock tbi can take
just curious how much power can stock 305 injectors, throttle body, computer, fuel pressure, and fuel pump support? Ive searched but havent found any answers
03-12-2008, 08:41 AM
#2
Moderator
iTrader: (1)
Join Date: Mar 2002
Location: Chasing Electrons
Posts: 18,405
Likes: 0
Received 216 Likes
on
202 Posts
Car: check
Engine: check
Transmission: check
Re: faq about how much power stock tbi can take
Stock stock? Completely stock? About 220 HP max'd out. About 188 HP keeping the injector DC% reasonable.
RBob.
RBob.
03-12-2008, 12:04 PM
#4
Member
Join Date: Jan 2008
Location: funro loserana
Posts: 218
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 rs
Engine: tbi 350
Transmission: 700r/manual
Axle/Gears: 3.23
Re: faq about how much power stock tbi can take
I read a while back that its about 220fwhp with stock injectors at 15 psi.
03-12-2008, 12:12 PM
#5
Member
Join Date: Jan 2008
Location: funro loserana
Posts: 218
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 rs
Engine: tbi 350
Transmission: 700r/manual
Axle/Gears: 3.23
Re: faq about how much power stock tbi can take
With my only mods being14x3 breather, 15 lb fp, and no muffler I dynod 176rwhp.
03-12-2008, 12:44 PM
#6
Re: faq about how much power stock tbi can take
i sprayed the ***** of my engine , stock EVERYTHING, cept for the 14x3 aircleaner, and the nitrous, and et' tells me somewhere in the 310hp range.
so id say north of 300hp if you went all out with the nitrous.
so id say north of 300hp if you went all out with the nitrous.
Trending Topics
03-12-2008, 11:50 PM
#8
Senior Member
Join Date: Jul 2007
Location: Manchester, CT + Nashua, NH
Posts: 1,461
Likes: 0
Received 1 Like
on
1 Post
Car: 90 Firebird Formula
Engine: LO3
Transmission: T5
Axle/Gears: 3.08 one wheel peel
Re: faq about how much power stock tbi can take
I dont understand... What is there limiting the LO3 to such low HP numbers? I thought the stock TB could support like 300 HP or something? Is it just the injectors??
03-13-2008, 02:37 AM
#9
Supreme Member
iTrader: (4)
Join Date: Nov 2005
Location: Sacramento
Posts: 1,946
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Re: faq about how much power stock tbi can take
Its when you run fuel pressure up to between 15 and 20 PSI or more and/or run larger injectors that you can support 300 - maybe 400 horsepower with tuning.
03-13-2008, 06:23 AM
#10
Supreme Member
iTrader: (2)
Join Date: Jan 2005
Location: Hurst, Texas
Posts: 10,037
Received 394 Likes
on
336 Posts
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: faq about how much power stock tbi can take
The problem is stock fueling. Stock fuel pressure is ~12 PSI. If you want any more than that you need to change the fuel pump. At that pressure the L03 injectors can't support much more than the stock 170hp. I run a bolt-on L05 with tuning and my fuel injectors are getting up over 95% duty cycle by about 4200 RPM on stock 12 PSI. It's really the fuel pressure that is limiting.
Its when you run fuel pressure up to between 15 and 20 PSI or more and/or run larger injectors that you can support 300 - maybe 400 horsepower with tuning.
Its when you run fuel pressure up to between 15 and 20 PSI or more and/or run larger injectors that you can support 300 - maybe 400 horsepower with tuning.
The stock throttle body flows reasonably well to 300 hp. With ultimate TBI mods and a pod spacer, it flows decently to about 320 FWHP. Above that a Bored out TBI or a 454 TBI is needed.
03-13-2008, 09:02 AM
#12
Moderator
iTrader: (1)
Join Date: Mar 2002
Location: Chasing Electrons
Posts: 18,405
Likes: 0
Received 216 Likes
on
202 Posts
Car: check
Engine: check
Transmission: check
Re: faq about how much power stock tbi can take
That would be engine HP (fwhp). What I did was to take the 55 #/hr that the injectors flow (all stock), multiply by 2 for 2 injectors, then divide by 0.50 for the BSFC (or just multiply 55 * 4).
That gives 220 HP, flywheel.
Then to factor in the DC% at 85, multiply 220 by .85. That gives the 188 HP.
RBob.
That gives 220 HP, flywheel.
Then to factor in the DC% at 85, multiply 220 by .85. That gives the 188 HP.
RBob.
03-13-2008, 10:50 AM
#13
Re: faq about how much power stock tbi can take
check this out:
it takes into account DC, BSFC, FP, CID, inj size in lbs or grams and calc's BPW.
http://www.users.bigpond.net.au/ben_...ctorsizing.xls
it takes into account DC, BSFC, FP, CID, inj size in lbs or grams and calc's BPW.
http://www.users.bigpond.net.au/ben_...ctorsizing.xls
03-13-2008, 12:02 PM
#14
Supreme Member
Thread Starter
iTrader: (4)
Join Date: Aug 2004
Location: southern maryland
Posts: 1,417
Likes: 0
Received 0 Likes
on
0 Posts
Car: 2012 Ram express
Engine: 5.7 hemi
Transmission: auto
Axle/Gears: 3.55
Re: faq about how much power stock tbi can take
do you have to get adjustable fpr or can u just put a different spring in the stock one for more pressure.
03-13-2008, 12:33 PM
#15
Moderator
iTrader: (1)
Join Date: Mar 2002
Location: Chasing Electrons
Posts: 18,405
Likes: 0
Received 216 Likes
on
202 Posts
Car: check
Engine: check
Transmission: check
Re: faq about how much power stock tbi can take
You can change the springs in the stock FPR for more pressure. Can also make it adjustable. Although a particular spring will only have a certain range of adjustability.
RBob.
RBob.
03-13-2008, 02:24 PM
#16
Supreme Member
iTrader: (4)
Join Date: Nov 2005
Location: Sacramento
Posts: 1,946
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 RS
Engine: 350 TBI
Transmission: WC T5
Axle/Gears: 3.42 Posi
Re: faq about how much power stock tbi can take
68# police car injectors at 45 psi will support about 485 FWHP keeping the duty cycle at a reasonable 80%.
The stock throttle body flows reasonably well to 300 hp. With ultimate TBI mods and a pod spacer, it flows decently to about 320 FWHP. Above that a Bored out TBI or a 454 TBI is needed.
The stock throttle body flows reasonably well to 300 hp. With ultimate TBI mods and a pod spacer, it flows decently to about 320 FWHP. Above that a Bored out TBI or a 454 TBI is needed.
03-14-2008, 10:13 AM
#18
Member
Join Date: Jan 2008
Location: funro loserana
Posts: 218
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 rs
Engine: tbi 350
Transmission: 700r/manual
Axle/Gears: 3.23
Re: faq about how much power stock tbi can take
Wow! Thats impressive, is that naturally aspirated?
03-14-2008, 12:02 PM
#19
Supreme Member
Thread Starter
iTrader: (4)
Join Date: Aug 2004
Location: southern maryland
Posts: 1,417
Likes: 0
Received 0 Likes
on
0 Posts
Car: 2012 Ram express
Engine: 5.7 hemi
Transmission: auto
Axle/Gears: 3.55
Re: faq about how much power stock tbi can take
were can u get these springs what ones do u recommend i would like to see 15psi outof the stock pump if possible
03-14-2008, 03:11 PM
#22
Re: faq about how much power stock tbi can take
It would work for that application too. I run a VAFPR but I am not using that feature(yet). I have the stronger spring of two in Aero unit set to 19 lbs. VAFPR offers max pressure at WOT and reduces the FP to improve the idle pulse width(larger pulse width).
03-14-2008, 10:18 PM
#23
Member
iTrader: (2)
Join Date: Feb 2008
Location: Conroe, TX
Posts: 294
Likes: 0
Received 0 Likes
on
0 Posts
Car: '70 Bronco, '91 Firebird, '03 Chevy
Engine: roller 302, 350 TB, stock 6.0
Transmission: NP435 Granny 4 spd, 700R4, 4L80E
Axle/Gears: 4.56 spool, 2.73 open, 4.10 broken
Re: faq about how much power stock tbi can take
Ok, so where do you find (or how do you make) a VAFPR?
03-15-2008, 12:23 AM
#24
Senior Member
Join Date: Jul 2007
Location: Manchester, CT + Nashua, NH
Posts: 1,461
Likes: 0
Received 1 Like
on
1 Post
Car: 90 Firebird Formula
Engine: LO3
Transmission: T5
Axle/Gears: 3.08 one wheel peel
Re: faq about how much power stock tbi can take
Aeromotive sells a nice one
03-15-2008, 03:12 PM
#25
Senior Member
Join Date: Jun 2007
Location: Akron, Ohio
Posts: 600
Likes: 0
Received 0 Likes
on
0 Posts
Car: 87 Suburban 2500
Engine: 455 Wildcat ( somewhat modified ))
Transmission: TH400 ( for now )
Axle/Gears: 4.10 ( for now )
Re: faq about how much power stock tbi can take
Needed a booster pump, as the stock pump contains a blow-off at about 14 PSI.
03-17-2008, 09:25 AM
#26
Re: faq about how much power stock tbi can take
GM "used" to sell one. I hear it is discontinued? I bet they are available somewhere? Try Ebay. I have the part # at home. I would think any manufacturer sells their own aftermarket VAFPR. Mine is Aeromotive unit. Very nice but a bit costly. I chose it since it offers two springs 10-20 and 20-60.
Thread
Thread Starter
Forum
Replies
Last Post
