Race Fuel??
 

Well, it looks like I will finally have a chance to get the car out after the upgrades to see how much they helped.

To really see what the power difference is, the best way is....

....yes a drag strip...

If the trap speed goes up power went up. Those are real world numbers. I wont abuse the thing off the line but and more looking for trap speed.

My thought is since it is a "new setup" maybe I should run some race fuel. "testing" on the street I have no indications of knock, but maybe mixing some VP100 with the pump gas would give a safety margin.

Now, I would really like to get out and try the car with the 100% race fuel and more boost or E85 and more boost but for a first time out, i think just running the "street" boost is the way to go...

Of course the one of the closest stations to my house has E85 pumps so that could be my "street boost".

-Dana

Did you specifically convert your fuel system for E85 use? If not, you can't safely use E85, as it will cause corrosion and kill your fuel pump.

^^Funny how there are lots of people running on E85 without doing any major hardware changes. You do of course need some software changes and possibly increase inj and fpr.

Bollocks.
E85 here for years, no such corrosion.

Lol, 'BOLLOCKS'. You've been watching too many Guy Ritchie movies Rogue!

Haha :cheers:

Dana, what mods have you recently added? When are you going to the dyno or strip?

Dana:

As mentioned, with E85 you will have to adjust your a/f about 15-20%. If it were me, I would want to keep the variables to a min for testing. Just run some race gas/xylene, etc for a safety margin without making any adjustments.

Then, run E85 and adjust a/f accordingly after testing is done; and crank up the boost!!! :)

The E85 should be a "flick of a switch" away. I have the Vitesse V-flex software so there is already E85 setting they are just "experimental".

Since i just got the AFR meter in, I havent had time to play with anything except pump fuel. When I "flick the switch" to E85 it adds lots of fuel and with gas it goes really rich.

-Dana

E85's biggest issue in a production environment is seat wear. On the valves AND the inserts. Gasoline contains some natural lubricants, E85 does not. It can also attack the back side of the insert where it meets the pocket in the head. Again, this is in a production enviroment, where you expect hard components to last he life of the vehicle. As E85 is hydrophillic, it can absorb water, which can lead to corrosion, but it is not a widely seen thing.

A/F is very different. I don't recall the gasoline numbers, but compared to octane, it takes 4.17 times as may moles of ethanol as octane, which translates into 1.68 times as much ethanol by volume, which translates into 1.58 times as much ethanol by mass. Having said that, that is stoich. What works in ethanol's favor is that it doesn't need the kind of enrichment gasoline does to make max torque. I had run these numbers for fuel economy, rather than max power, and they boxed closely with the development engines.

Anyway, you can run the numbers yourself, or you can talk nice to Rogue or some of the others, and they might share. But you need to make some big time fuel calibration changes to run E85. To take full advantage of it, you should increase your CR.

king, while normally i wouldnt question your experience (heard another 5.0 yesterday....ahhhh!), i thought the gasoline lubricants were in the days of leaded gas?

In leaded gas, lead was the lubricant. E85 is very dry.

Just throw some 2 stroke oil in it. Should be fine. DON"T DO THIS as it was a joke.

Ok, if you are already mapped for it then you will be fine.

I think every day that E85 is not close distance to me I die a little inside... LOL

:rolleyes:

Dana, I wish you luck in whatever direction you go with.. When are you thinking of goingup??

I am possibly going to head up on Weds if everything goes OK this week.

Lead made life easy on everyone. I don't think they even had to harden the seats (later iron heads used induction hardening to harden the parent metal). But unleaded does still provide some librication. Ethanol is another matter entirely.

I think the E85 issue is that it does require a MINIMUM amount of "best practices" to have a long term success. Rubber does need to go in the long run, as over time I think that the ethanol will not dissolve, but soften the material and cause issues. Just to be safe, I am using SS hardline instead of aluminum, and any softline that I use will either be teflon lined (ultra flex 650, goodridge teflon bore, etc) or rated for E85 (supposedly, Twist-lok from russel is approved)

This wednesday. I am actually home on a weekday.

I hope to be there when the gates open at 4.

-Dana

Crap - I'm not going to be ready to run... But I'll try to make it anyway if you guys are going.

Probably not going to be coming up early at all. Manning the shop solo this week and getting behind already...If I come up, it will be later.

I am leaving around 3pm to get there. Hope to see you guys.

-Dana

I'm not making it. My better half just got a new job, so we are out to celebrate!

Nice to see you again Dana,

didn't get to stick around and see what it did on the last run (assuming last run since there was an oil down and we left ).

Looked like you were creeping up on it pretty well. Gonna try harder to make time next week to bring mine up. Or see if someone is doing a private tune session soon.

Ok, so what times/speeds?

Times....too embarrassing...best was a 14.7 with lots of wheel spin.

MPH was 103 on 15psi.

But what I must say is the night was a great night in the fact that there was some good troubleshooting.

Sid. I owe you beer.....with any luck no damage was done to the turbocharger and if it is OK you saved me long term damage. It will take a little bit to see if the turbo is OK. Thanks!!

-Dana

What happened?

Ha - don't be embarrassed. Everyone thinks that straight-line racing is easy, but that simply isn't true. AND up here at altitude, expect your times to be ~1 second slower then sea-level.

BTW if your 15psi of boost is a gauge reading, then your really only running ~12psi. We lose ~3psi up here...

Life's tough at the 'top'.....;)

I remember running my turbo cars with a MAF up to 8500’ and the boost were the same in LA and in Greer, AZ at 8500'. I'm now using MAP, and it's the same. If you are running MAF or MAP, the turbo will be running harder at altitude, but should produce the same boost whether at sea level or at 9000' to its max capability of producing boost. The original barn door intake of the 951 may not do well at altitude, but I'm not one to know. I do know that it opens based on pressure, so I'd assume this old school metering would be similar to MAF or MAP.

Granted the turbo is boosting thinner air, and spinning faster at the same boost levels as at sea level, but your boost gauge should register boost pressure accurately whether at sea level or in mile high country. If I lived at 5280' or above, I would have a slightly larger turbo than what would be necessary at sea level (assuming similar real world consistent HP) to compensate for the thinner air. More lag, but similar top tq and HP, with max TQ being later in the RPM's. Top end HP would be similar when using the same motor.

What you will find is there is more lag on a turbo car at altitude. It's harder to compress thinner air, hence more lag. Small turbo gas 4 stroke airplane motors like what is in the good old Cessna 210T Centurion have similar HP at sea level up to 28,000' because of the use of a turbo. Realize the power drops after 17,000', but that's much higher than any 951 or most cars care to take a spin.

It's the lag of the turbo trying to compress thinner air, and the later rpm onset of tq that makes any turbo car slower at altitude.

If your gauge is accurate, you are getting what it states in terms of boost readings going into your manifold.

I'm getting really quite tired of this old misnomer.

https://rennlist.com/forums/7029239-post42.html

https://rennlist.com/forums/5622707-post207.html

https://rennlist.com/forums/4693930-post6.html

https://rennlist.com/forums/4333882-post62.html

Gauge pressure != absolute pressure. There is a reason why things are labeled Psig or Psia. Gauge pressure is differential, and will NOT show the ~3psi loss of air pressure up here. Absolute pressure, obviously, will show the lower air pressure.

Here is a good page showing the pressure difference:

http://www.crh.noaa.gov/bou/include/...webpres_16.txt

The first one, Denver Intl Airport, atmospheric pressure is 12.127psi. The mean sea level pressure is 14.676psi. A 2.549psi difference. But normal boost/vacuum gauges are not going to read -2.6psi with the engine off. No, they will read 0 - because they measure the pressure differential between manifold and atmosphere.
So, if the gauge reads 15psi boost, then that is the difference between manifold and atmosphere, which the sum is 27.127psia. The same car at sea level, running 15psi of boost (the difference between manifold and atmosphere), the total is 29.676psia. Obviously the difference is in the starting pressure, IE atmosphere.

Compared to sea level, at the same gauge pressure, we at altitude are running less absolute pressure, nearly 3psi.

:crying: You said it :burnout:

Most turbo applications are set to read boost for absolute pressure, and compensate for density. I'm not going to argue with you here, as you are probably someone I'd enjoy spending time, as we have similar interest in cars.

Maybe it's my personal experience with my turbo cars, and how they are set up to read boost pressure. I used to have a S4 TT and here is a quote:

The audi computer has altitude correction built in, so at 5000 ft, the
boost is increased from .425 to .575 (yo, that's audi-eeez, so +/- .0250 is
allowed, took mean for all calculations)... So, with the guage reading .845,
add the .575 = 1.42 absolute... Translating this, the MC motor will be
99.64% HP efficient (and given the altitude pressure table variance of +/-
.0250 of mean, 100% is within spec) of sea level HP @ 5000ft.... All other
things be equal (caveat), there should be NO DIFFERENCE IN POWER LEVELS
BETWEEN YOUR CAR IN CO OR AT SEA LEVEL.

Here is a chart to verify your previous post. I get this, but my issue here is that my turbo is boosting harder in Greer than in Tucson, I can hear it, and my boost guage reads the same. I do have a TEC stand alone, and I know it has altitude correction built into it's software. Maybe my old 951 cars didn't have this, and I'm mistaken with my previous post.


Altitude Air pressure (in. Hg) Air pressure (psi) Loss as referenced to sea level
(psi)
Sea level 29.92 14.7 0
1000 ft 28.86 14.18 -0.52
2000 ft 27.82 13.67 -1.03
3000 ft 26.81 13.17 -1.53
4000 ft 25.84 12.7 -2
5000 ft 24.9 12.23 -2.47
6000 ft 23.98 11.78 -2.92
7000 ft 23.09 11.34 -3.36
8000 ft 22.23 10.92 -3.78
9000 ft 21.39 10.51 -4.19
10000 ft 20.58 10.11 -4.59

I'll verify my thoughts tomorrow with folks much better educated than me in the science of this subject tomorrow.

Thanks for making me think about what I may not know.

Kindest Regards,

George

Here is where I don't think I have been able to clearly get my point across.

You are correct, the boost control system is different in your S4 than most 951s.
What kind of boost gauge do you use? If you use an absolute gauge, then your gauge will read "correctly". However, a normal (autometer, ect) type of gauge fail to account for the less starting air pressure.

So if I have a absolute boost control, like your TEC, and have a normal autometer gauge, and set the boost to 15psi at sea level then drive to Denver, the absolute boost controller is going to increase the boost pressure to compensate (your Audi quote verifies this). Now that you're in Denver, you will be running the same absolute pressure, but the autometer gauge will show ~3psi more boost then it did at sea level.

Also, the "NO DIFFERENCE IN POWER LEVELS BETWEEN YOUR CAR IN CO OR AT SEA LEVEL" is not quite true either. The simple fact that the turbo has to make up the lost pressure means more work is being done. And work isn't free; this can be seen by a reduction in VE.

The best I could manage here in Michigan with my old 1987 951 (Autothority Stage 2 Chips & Banjo Bolt, 245's) was a 14.1@103 with a 2.7s 60ft. I was either spinning the tires or bogging down and waiting for the turbo to spool every launch.

Im taking my 1988 951 out next Friday, it has a few goodies

LR MAF, 951 MAX Chips, Powerperfect, Super 61-1, 55# Injectors, 3.0 BAR FPR, Dual Port Wastegate, WBO2, Full 3" Exhaust, LSD etc....

Im aiming for 12's

The 60ft of the 951 will always kill any 0-60 or 1/4 mile times. I think the fastest 60 fit I ever saw a 951 pull was 2.1 or 2.2.

Although that has always let me beat much faster 1/4 mile cars in simulated roll races. ;)

"yea, its only a low 13 sec car at best" lol But then in a 20 or 40 roll I can stay with mid 12 sec cars :)

The absolute / relative is a question that 951 people dont fully understand.

To make matters worse I am running the Wastegate off of a MAP sensor (which references to vacuum and therefore reads the same regardless of altitude). Logging the MAP sensor with the car off (i.e. atmospheric pressure, it is about 800mbar).

I have not set the turbo boost using the MAP yet. It has been set based upon an relative boost gauge. I am at about 16-17psi on that gauge.

I have to hook up the zeitronix to log boost a (from the MAP) and RPM. So far it is only hooked up for AFR. Need a little more time to get things done


So, I am still running the car conservative until I get things dialed in. For the first outings, it best not to crank boost up until the head gasket blows and then back it off one psi.....

-Dana

What!!! Heresy!

just to touch on the subject lightly.

What seems to be forgotten whenever this subject comes up is how dramatic the lack of pressure is on a turbo car at elevation. I'm sure everyone here has sat and watched the gauge and wait for it to start building boost, then once it hits 1 psi it takes off on about any turbo charger. There is no diffence up here in that regard it is just that it ,takes longer,uses more mechanical enery, creates more heat = power loss.

On a 951 this is more pronounced due to the turbo positioning. It is always an intereseting conversation.

Now since this subject has come up it brings me to why I didn't take my car up... playing with the anti lag too much and blowing out the turbo flange gasket :-(. Hoping it will negate most of the altitude issues

next week maybe.

What is this magical thing you speak of??? Please tell us more. :)

i know a guy that runs up pikes peak for the hill climb and he says he has a switch for higher boost when he gets to the top

Yup, you can run more boost at altitude. Some filling stations at high elevations don't sell premium gas. You don't need as much octane at high elevations. I still keep my car set the same. Don't want any more EXPENSIVE issues.

Ok.

SId, I must say thank you many times. Your showing up there and giving me advice saved a brand new turbo from ruin.

-Dana