Login    Forum    Search    FAQ

Board index » Racing Forum » E85 Fuel Systems




Post new topic Reply to topic  [ 57 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
 Post subject: Re: E85 test
 Post Posted: Thu Oct 04, 2012 7:18 pm 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
So by lowering the iab he made the idle rich and that changed the T-slot jetting??

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Thu Oct 04, 2012 7:52 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
Yes a smaller IAB enriches the T-slot.
The IAB controls the vacuum thats present in the drillings of the circuit. It works in conjunction with the T-slot and the closed throttle blade position. When the blade is closed the amount of T-slot exposed above the minimum restriction point of the thickness of the blade becomes an air leak into the circuit. If you epoxy up the top part of the slot the mixture will be richer whenever the blade is exposing some of the slot to the atmospheric pressure. The slot supplies fuel until an arbitrary point when the blade is too far away. The slot supplies fuel even when the blade is way past the top of the slot.
The booster supplies fuel once the vacuum it generates is enough to lift the fuel to the height of the booster feed tube, then the fuel flows from the booster. The start of the booster flow is erratic and its the T-slot that has to supply a consistency to the mixture. If the IAB is too large during this phase the flow from the T-slot will reduce too much and the engine will lean out. The reason why it reduces T-slot flow is because you have emulsion taking effect in the main well. The main thing that pushes the fuel toward the outlet of the booster is the emulsion air flow that going through the top e-bleed. The fuel level is critical in the operation of this bleed. If you block the HSAB the booster flow starts a lot later in the CFM flow range, its that late the T-slot cannot cover it. Do the test yourself with a ball point pen and block the HSAB. Once there is emulsion air present in the main well it has an effect on the T-slot flow, because once the emulsion starts to blow air through the top e-bleed the head (a word for pressure) thats exerted on the IFR starts to reduce. Remember emulsion air reduces the density of the fuel in the well and its the density of the fuel that determines its head upon the IFR. So' the fuel flow rate through the idle circuit drops, this can be altered by choice of IAB etc. This is the reason why the lower location for the IFR is better than the high location favored by some special people. The high location subjects the IFR to a range of head approaching zero whereas the lower location is always a reasonable pressure, so the IFR stays in turbulent flow within the jet passage itself. Its all about the differences in flow rate or the fuel supply between laminar and turbulent.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Thu Oct 04, 2012 9:15 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
When you change the main jet size it does have an effect on the idle and the T-slot. The main jet size influences the volume of emulsion air. Smaller main jet = greater emulsion flow. If you are using a carby in a race car that requires a main jet thats larger than 6 sizes from the stock Holley then you are starting to alter the relationship of emulsion and T-slot to booster.
The main jet even though its larger than 4 times the IFR still alters the flow into the main well once the emulsion has started. Consider the emulsion this way, the air flowing through the e-bleeds is in effect trying to prevent the fuel level from being any higher than the height of the bleed. Its the main jet that allows it to keep filling up thus fuel flows. Its the difference in head between the main well and the bowl that controls the main jet flow. That's why fuel pressure control and level is important. if the fuel pressure fluctuates the head differential fluctuates and the mixture fluctuates. The more emulsion air you use the less effect fluctuation has upon the final mixture.

When you dont accurately adjust the idle mixture and the t-slot mixture of your racing car you leave top end power on the table. The top end power is effected by the technique used in the idle circuitry. The standard Holley technique is a good one, Its best not to over think it or stuff with it too much. The main problem with the carbys is the T-slot is made different sizes on the same carby, there quality control is terrible. It is necessary to have the low speed circuit setup so that the idle screw is around 1.5 turns out and the t-slot is providing a nice controlled mixture. You can test t-slot mixture this way. Engine in neutral, rev it up to just under booster flow and then shut the throttle quickly. If the engine slows down momentarily to RPM that's below idle its too rich on the slot. If its too rich the engine will slow down then pick up again and idle. Its sort of a dip in the RPM. the engine should just come back to idle and stay solid at that RPM. If you do this test by bring it higher in the revs so its booster flowing and its dips the RPM on the return, its the same thing, its too rich somewhere, most likely the booster emulsion.

Heres a common scenario, suppose your using lots of emulsion air and artificially pulling the fuel low in the well by doing that, thus your main jet can be smaller. The problem is then that the fuel head in the main well is not enough to prevent air entering the slot and flowing backwards into the main well. This air enters at the base of the main well far below the e-bleeds thus it pulls the fuel level even lower in the well. The outcome could be slugging flow or not. Slugging flow will still supply enough fuel to maintain the AFR but it enters the air stream in lumps and there are dry parcels of air between the lumps. The cylinders receive a less homogenous mixture and your power goes away. Your wideband reads a richer mixture because its a CO sensitive device and poor homogenization creates excess CO, so you think it needs a top end lean out, you do that and it goes better but its not the ultimate and you never find out because you think you have it all correct because the stupid WB says so.
There really is no way for the average racer to figure out if this is happening or not, you need a gas bench and dyno to do it. But you can prevent it by using the setups here in this forum and tune with minimal emulsion air. The emulsion air needs to be enough to do the job required and no more. Sneaking up on it is better than wholesale changes.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 7:39 am 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
Keith sorry for taking over your post but as I read this a few times my head is starting to slow down from spinning #-o ..

Ok now with my 1250 with T-slot already exposed with the blades closed and holes in the blades I have to say it's close to where it need to be.........maybe........I have reduced the T-slot from .084 to .081 and did see some difference in Idle and also filed down the acc. pump cams a bit to try to "clean" up the rich dip on the hit. It's a lot better and wanted to try going from the 45 discharge nozzle to a 42 to see if it will respond to that or bog at the hit.. That I could try in the pits maybe..
I like the idle test with the dipping of the idle...Have to try that but thought I was ok as it needs some throttle when it's first started to keep it running...
Now is this basically the same for gas as for E85???

Thanks Bruce...good reading..

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 8:26 am 
Offline
Site Admin
User avatar

Joined: Tue Apr 18, 2006 6:38 am
Posts: 11804
Location: Coming At Ya!
Since you're talking about shooters, after I got that other methanol 1150 running (B carb) I wound up with .035 shooters in it where the original methanol 1150 (A Carb) has .062s? Had NO "T" slots expose on the B carb and wound up lengthening them just to the edge of butterflies @ normal idle setting. Then I filed the butterflies lower edge to gain the "square" T slot window below them.

That B carb will go off the Pro Stage @ around 1500 RPM with no stumble at all and is much better than the A carb at part throttle response. The A carb has too much slot and drilled butterflies and it requires about 2K RPM at the hit or it sometimes falls flat on it's face.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 8:41 am 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
Beretta wrote:
Now is this basically the same for gas as for E85???


Petrol is very reactive to stuff like that, Alcohol fuels are not so because there are 2 ways to burn an alcohol. You can either use all the molecule and make CO into CO2 etc or you can just use the Hydrogen and only make water and waste the CO part of the alcohol. With E85 you may have a bit of both as far as if you can detect the idle test etc. Just give it a go and see what happens. You dont have to change your tuneup just because of this, but start putting things together to form a picture of whats going on inside the engine. Thats what I do, Each engine eventually forms a personality to me


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 4:28 pm 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
Ken0069 wrote:
Since you're talking about shooters, after I got that other methanol 1150 running (B carb) I wound up with .035 shooters in it where the original methanol 1150 (A Carb) has .062s? Had NO "T" slots expose on the B carb and wound up lengthening them just to the edge of butterflies @ normal idle setting. Then I filed the butterflies lower edge to gain the "square" T slot window below them.

That B carb will go off the Pro Stage @ around 1500 RPM with no stumble at all and is much better than the A carb at part throttle response. The A carb has too much slot and drilled butterflies and it requires about 2K RPM at the hit or it sometimes falls flat on it's face.



This should be over in the fuel section instead of here but..
I remember talking to you about this :-k .........But my question is WHY?????
Could it be the arrangement of the banjo's being shortened?? Or what??????
And I am sure you would like the other 1150 (A carb) to be just as responsive..

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 7:40 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
The response comes from correct mixture running on the T-slot and not relying on accelerator pumps. When the engine is running correctly on a t-slot the fuel mixture is correct all the way through the manifold system and into the cylinders, when you have to rely on pump shot its not. Kens A carby he says has too much slot and drilled butterfly's so I would assume that to mean the slot exposed below the blades is about right but there is too much above the blade. Read what I said about the slot above the blade and its effect on the vacuum in the drilling's. If its leaking too much air into the circuit The IFR has to either be bigger to obtain an idle or you just put up with it running a bit lean. Either way its not going to respond because the GOOD mixture isnt present in the manifold runners etc. The art of t-slot setting is to get an IFR that coves the range without having to resort to a small IAB. There are many arrangements of t-slot, they can be a series of holes or a shaped slot or a combination of both. Sometimes I have to add a hole next to a slot, sometimes I change the shape of the slot making it wider at the bottom or the top, depends on the requirements. But I never drill a hole in a butterfly. Drilling holes gets you a quick fix but it doesn't get you correct mixture for response.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 7:42 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
The t-slot is a miniature slide carburetor. The IFR is the main jet, the IAB is the venturi, the blade edge is the slide.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Fri Oct 05, 2012 7:51 pm 
Offline

Joined: Sun Jul 10, 2011 6:32 pm
Posts: 24
Location: Central Oregon
Barry, No problem. You've all got me thinking more about some stuff I hadn't really thought about! I'm reading some of this stuff over and over trying relate it to my own stuff.

_________________
Keith


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Sat Oct 06, 2012 7:08 am 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
shrinker wrote:
The response comes from correct mixture running on the T-slot and not relying on accelerator pumps. When the engine is running correctly on a t-slot the fuel mixture is correct all the way through the manifold system and into the cylinders, when you have to rely on pump shot its not. Kens A carby he says has too much slot and drilled butterfly's so I would assume that to mean the slot exposed below the blades is about right but there is too much above the blade. Read what I said about the slot above the blade and its effect on the vacuum in the drilling's. If its leaking too much air into the circuit The IFR has to either be bigger to obtain an idle or you just put up with it running a bit lean. Either way its not going to respond because the GOOD mixture isnt present in the manifold runners etc. The art of t-slot setting is to get an IFR that coves the range without having to resort to a small IAB. There are many arrangements of t-slot, they can be a series of holes or a shaped slot or a combination of both. Sometimes I have to add a hole next to a slot, sometimes I change the shape of the slot making it wider at the bottom or the top, depends on the requirements. But I never drill a hole in a butterfly. Drilling holes gets you a quick fix but it doesn't get you correct mixture for response.


Interesting Bruce, Question for you how big (CI) is the average motor you work on??
So what your saying is that the T-slot will have to in a different position on just about every motor. As there going to need a different amount of blade set for idle..

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Sat Oct 06, 2012 7:41 am 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
The average engine in Australia is 350 chev or 351 clevo or a stroker version of either. Most BB's are rarely over 460 cubes. The race engines I work on make 800 plus hp NA. Blown ones are more. I have fitted single 4BBL smartcarbys on up to 830hp engines. They dont have holes in the butterflys. The blades are very closed. When the mixture is controlled properly in the idle circuit the amount of blade opening needed is very small. I cannot get Holleys to idle as well as my carby. My carby is a divorced idle circuit, that means it is independent of the mains just like some European carbys. Divorced idle circuits cannot bleed air backwards at any time, they always flow fuel. So you have more freedom in what you do with slot design, you just cant make a mistake up in the revs etc.
Within the Holley design there is limited options for tuning of the idle circuit. Its so interactive with the emulsion and booster signal that it complicates matters.


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Sat Oct 06, 2012 7:56 am 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
Care to share some pictures of your smartcarb?? And just how big do you make them??

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Sat Oct 06, 2012 8:28 am 
Offline
User avatar

Joined: Mon Oct 29, 2007 7:07 pm
Posts: 1422
Location: Florida
http://www.smartcarby.com


Top 
 Profile  
 
 Post subject: Re: E85 test
 Post Posted: Sat Oct 06, 2012 12:45 pm 
Offline
User avatar

Joined: Wed Apr 19, 2006 8:20 pm
Posts: 5852
Location: N.J.
Good looking carb Bruce. Looks like all billet aluminum and the top of it looks like the one Pro systems has on there SV carb.
Do you have any of them over here...

_________________
Image
running E85
Best ET 8.07
Best MPH 170.71
Barry


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Post new topic Reply to topic  [ 57 posts ]  Go to page Previous  1, 2, 3, 4  Next

Board index » Racing Forum » E85 Fuel Systems


Who is online

Users browsing this forum: No registered users and 1 guest

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
cron