Holbert Car fuel pressure measured 1st time
11-06-2006 | 08:54 PM
#17
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From: saratoga, ca
180mph was the run at Nardo the march before the August 172mph record run.(actually, on my birthday August 7th 1986 in Bonneville!)
Dont think the pistons or heads were modified too much, as the exhaust ports were still stock looking and compression tests have always been 180psi per hole, and real even across.
Mk
Dont think the pistons or heads were modified too much, as the exhaust ports were still stock looking and compression tests have always been 180psi per hole, and real even across.
Mk
Originally Posted by IcemanG17
MK
Did the Holbert car really hit 188 at Nardo?? Like Bill says stock S4 autos have hit 165-168 with cats and mirrors at the same altitude.....assuming those 928's were 260ish WHP....and your was 285whp (original config)......I would guess 175 was doable (without mirrors).....
BUT.....there is something special about that engine.....I wouldn't be surprised if it has higher comp pistons, slight head work....or something
Did the Holbert car really hit 188 at Nardo?? Like Bill says stock S4 autos have hit 165-168 with cats and mirrors at the same altitude.....assuming those 928's were 260ish WHP....and your was 285whp (original config)......I would guess 175 was doable (without mirrors).....
BUT.....there is something special about that engine.....I wouldn't be surprised if it has higher comp pistons, slight head work....or something
11-06-2006 | 10:18 PM
#18
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From: Southern Alberta, Canada
Originally Posted by mark kibort
No changes other than slapping the fuel pressure guage on .I wanted to get a baseline for pressure, especially since we are going to be swapping engines over the winter.
Guys, ive dynoed the car MANY times over the last 5 years, always paying close attention to fuel ratios. 12.5 -13:1 over the entire rpm range to near redline.
stock, it was very close to the 14:1 range before the regulator was added (RRFR). plugs look great, and last an entire season, always looking blackish grey. tail pipe has some black carbon on the inside, normal for race cars.
I just put the gauge on and i measured 72psi. i dont use the vacuum pressure pull back on the regulator. it runs fatter at idle, and a slightly higher idle speed, and i like this. (1krpms )
Jim, your right, we dont know the differences of the car on the inside of the engine, but we will find out soon! now that the cams are stock, its going to be interesting to see if anything else is different.
Im wondering why my pressure is so high. maybe the 1 or 1.5 turns i tweeked on the RRFR did this.
also, single fuel pump is the stock S4 type for which ever year used only one.
mk
edit : what are the lb flow ratings of the stock injectors? ive heard 19lb/hour
are the 84 US injectors much different? trying to coorelate what i knew with my old 293rwhp 5 liter US Ljet version with 53psi fuel pressure vs this newer S4 with 72psi and 320ish rwhp.
I think i bought the RRFR from Devek in the early days. remember, this was one of the main key mods (headers and RRFR) I dont know the difference between a AFR and a RRFR. anyway, its a standard type mod
Guys, ive dynoed the car MANY times over the last 5 years, always paying close attention to fuel ratios. 12.5 -13:1 over the entire rpm range to near redline.
stock, it was very close to the 14:1 range before the regulator was added (RRFR). plugs look great, and last an entire season, always looking blackish grey. tail pipe has some black carbon on the inside, normal for race cars.
I just put the gauge on and i measured 72psi. i dont use the vacuum pressure pull back on the regulator. it runs fatter at idle, and a slightly higher idle speed, and i like this. (1krpms )
Jim, your right, we dont know the differences of the car on the inside of the engine, but we will find out soon! now that the cams are stock, its going to be interesting to see if anything else is different.
Im wondering why my pressure is so high. maybe the 1 or 1.5 turns i tweeked on the RRFR did this.
also, single fuel pump is the stock S4 type for which ever year used only one.mk
edit : what are the lb flow ratings of the stock injectors? ive heard 19lb/hour
are the 84 US injectors much different? trying to coorelate what i knew with my old 293rwhp 5 liter US Ljet version with 53psi fuel pressure vs this newer S4 with 72psi and 320ish rwhp.
I think i bought the RRFR from Devek in the early days. remember, this was one of the main key mods (headers and RRFR) I dont know the difference between a AFR and a RRFR. anyway, its a standard type mod
55psi is stock without vacuum so at 72psi you have a 31% increase in FP. If you brought the FP down to stock it would be interesting to see the diff. in h/p.
Fat is good for safety but robs power...............I have boxes of main jets, slides, needles and pilots with corresponding weather data over the years at various race tracks as work that we used to do.
Easier today with a 'Shark Tuner'.
11-06-2006 | 10:48 PM
#19
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From: Not close enough to VIR.
Mark, Bosch injectors are rated at 3bar or 43.5psi. 87+ injectors are about 19lbs and all previous non-CIS injectors are about 24lbs (22-26 depending on which specs you use and how you estimate). As was mentioned, without vacuum, stock would be 55psi. Are you running 12.5-13.5 afr in just open loop, or both open and closed loop? If you're running that rich closed loop, the extra pressure is just pushing that injection system outside the range (5%?) that the O2 loop can adjust.
I remember it being 180-something.
I guess that's why my car feels like a dog after all the intake/vacuum leaks were fixed and was a rocket that would ping on 93 octane before the fixes. Hmm... must get lean for speed.
Originally Posted by IcemanG17
MK
Did the Holbert car really hit 188 at Nardo??
Did the Holbert car really hit 188 at Nardo??
Originally Posted by the flyin' scotsman
Fat is good for safety but robs power...............
11-06-2006 | 10:50 PM
#20
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From: saratoga, ca
not much robbing on the fat side of the curve . we saw only 3hp drop going from 12:5:1 to under 12:1 on my 84 5 liter Ljet system. on the other side of stoich, hp falls like a rock.
im not that fat now, its about right. its the reason it makes good safe power now.
I think i posted the last dyno. it seems that the engine wont go much richer than 12.5:1. I dont know what a full turn means in fuel ratio, but im sure its the differnce of stock vs what its at now!
Ill do some full throttle runs and see what the fuel pressure turns out to be. maybe ill hook up the vacuum too to see what that pulls back the pressure to.
mk
im not that fat now, its about right. its the reason it makes good safe power now.
I think i posted the last dyno. it seems that the engine wont go much richer than 12.5:1. I dont know what a full turn means in fuel ratio, but im sure its the differnce of stock vs what its at now!
Ill do some full throttle runs and see what the fuel pressure turns out to be. maybe ill hook up the vacuum too to see what that pulls back the pressure to.
mk
Originally Posted by the flyin' scotsman
Whats the chances of getting the car in its present state on a dyno and play with the FP?
55psi is stock without vacuum so at 72psi you have a 31% increase in FP. If you brought the FP down to stock it would be interesting to see the diff. in h/p.
Fat is good for safety but robs power...............I have boxes of main jets, slides, needles and pilots with corresponding weather data over the years at various race tracks as work that we used to do.
Easier today with a 'Shark Tuner'.
55psi is stock without vacuum so at 72psi you have a 31% increase in FP. If you brought the FP down to stock it would be interesting to see the diff. in h/p.
Fat is good for safety but robs power...............I have boxes of main jets, slides, needles and pilots with corresponding weather data over the years at various race tracks as work that we used to do.
Easier today with a 'Shark Tuner'.
11-07-2006 | 11:46 PM
#23
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Joined: Mar 2002
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From: California
Does anyone have the test data from Nardo? Exact speed would be great!
Susan and I had a great chat with the engineer responsuible for the aerodynamics of both the hobert car and the Havoline 962 a few years ago.....interesting tales!
Cheers,
Marc
Susan and I had a great chat with the engineer responsuible for the aerodynamics of both the hobert car and the Havoline 962 a few years ago.....interesting tales!
Cheers,
Marc
11-08-2006 | 12:33 AM
#24
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From: saratoga, ca
Do tell what he said!
Marc, does the 72psi sound unusually high for the RR fuel regulator i have?
Thanx,
Mk
Marc, does the 72psi sound unusually high for the RR fuel regulator i have?
Thanx,
Mk
Originally Posted by marc@DEVEK
Does anyone have the test data from Nardo? Exact speed would be great!
Susan and I had a great chat with the engineer responsuible for the aerodynamics of both the hobert car and the Havoline 962 a few years ago.....interesting tales!
Cheers,
Marc
Susan and I had a great chat with the engineer responsuible for the aerodynamics of both the hobert car and the Havoline 962 a few years ago.....interesting tales!
Cheers,
Marc