going to make the jump to E85, what injectors would work?

[CBR600RR]

Well i finaly decided to make the jump to E85, but im having trouble trying to figure out what size injectors to go with, and if my pump can handle what i want to run. right now im on 750cc's (i know thats not enough) and a walbro 255hp. Im running a precisions turbo T3/T4 60trim, 8.5:1 compression and i plan on putting a good amount of boost to in in the future, but currently at about 15psi. Ohh and have -6an from the pump to the rail with an AEM AFPR. would 1000cc be enough or should i go 1600cc?

[burnett03]

You are missing important details such as what you are using to tune? Dsmlink i hope. If so then i suggest 1600cc. I run 1000cc injectors and im at around 89% duty cycle, so i'd say it's safe to assume that you would be over 100% on a 60trim. The pump may or may not be enough. So far for me the walbro 255 is enough, but who knows what happens once i start spraying. I know you can get a bit more out of the walbro pumps on e-85 by lowering the base fuel pressure.

[Hemicolt]

I would say 1000's would be fine i run them and i make ok power and my duty cycle is 85% ....I would stay away from 1600's if you can driveabilty sucks on them...They have 1150's and 1200's too witch are another way to go and be plenty of injector for you...

[thiazole]

Technically, if 750s work on gasoline, then 1000s would work on E85 since 1000 is 33% bigger than 750 and you need about 30% more fuel for E85. A good rule of thumb that I just made up is if you take your max airflow in lbs/min and multiply that by 23, that is the minimum injector size that you need for E85 (ie, 40lbs/min X 23 = 920cc).

[Toybreaker]

Good Topic!

I'm researching this as well, although I'm looking at a much more humble power level then most of the other people who are making the switch.

There's much to learn on the topic, and I look forward to an intelligent discussion on the various brands of injectors, and correct injector sizing.

I know there's much to learn about spray patterns, and the atomization of e-85. (Yea, I know, it sprays out of the injector :rolleyes: )

Seriously, many of these high flow injectors are "modified" by tampering with the orifice size, and I'm not so sure that the efficiency matches the increase in size.

I'm not a tuner, (by any stretch of the imagination :p ) but, I've been noticing how different the injector on times are for the various people running big injectors on e-85. (at the ~same~ airflow rates)

Some people are maxing 1000cc injectors, and that just boggles my mind.

Other people are making really good power, with reasonable drive times, on that size, (and smaller).

That's very interesting to me.

Edit; I know some of that is due to differences in the fuel pressure they run. I'm curious what you guys are running for pressure.

I *believe* many of these big injectors are modified from the o.e. compressed natural gas line of injector design, and I'd be interested to hear educated imput on whether that matters or not. (I'd love to see the spray patterns of these units, compared to a more traditional injector)

I would also be interested to know if anyone is doing meaningfull research in whether there's any o.e. e-85 components that have any place in a modified dsm.

Ford and G.m. are making waves with their flex fuel vehicles, and they're gearing up to bring even more models to market

There's got to be some fairly high flow options from them, or their racing divisions. Those wily engineers know a thing or two, and I would imagine that an injector optimised for e-85 from the git go would be better than a modified unit. The orifice size and ditribution/spray pattern at high flow rates would certainly be more consistent than an injector that's had mean things done to it's orifice by an underpaid illegal in some back alley sweatshop.

It goes without saying that an o.e. injector meant for e-85 would certainly be ethanol tolerant, and that could go along way towards a consistent, trouble free system.

Does anybody on here have access to the factory specs on e-85 components from the manufacturers?

//subscibed

[thiazole]

I'm not a tuner, (by any stretch of the imagination :p ) but, I've been noticing how different the injector on times are for the various people running big injectors on e-85. (at the ~same~ airflow rates)

Some people are maxing 1000cc injectors, and that just boggles my mind.

Other people are making really good power, with reasonable drive times, on that size, (and smaller).



A lot of it is the a/f ratio you use. E85 seems to be very forgiving of lean tuning. I've found that my car runs very good with a WB reading just below 12:1, but I've seen people go as far as 13:1, and if you don't see knock or excessive combustion temps, then I guess why not? Other people try to be more conservative and run 10.5:1 (although I personally don't think there is any benefit to going below 11.5:1 on E85). If you think about the difference between 10.5:1 and 13:1, it is easy to see how one person is maxing out 1000s and making less HP than someone who is only seeing 75% injector duties.

Ethanol does have a significantly higher surface tension and latent heat of vaporization than gasoline, so I'm sure it doesn't atomize as easily as gasoline, so you have a good point. If I'm not mistaken (and I might be) FIC uses Ford injectors for some of their sizes, so if they are already using them, why not adapt some Flex Fuel injectors.

[v413nc3]

You need to be VERY careful with Ethanol. It will bend a rod long before you see knock. The added amount of fuel, and its ability to handle more latent charge heat will mean that if you get preignition (very easy to do on Ethanol and Methanol) long before your knock sensor picks up "knock". If it ever does. Tuning your engine off your knock sensor is like cooking your food off your smoke alarm.

[rodent]

What about the fuel pump for E85? Thinking of using 1600cc injectors with a big 16g on a stock engine (300ish hp). Will a Walbro 255 be enough? Whats the cut off for a 255?

[Cloud]

You need to be VERY careful with Ethanol. It will bend a rod long before you see knock. The added amount of fuel, and its ability to handle more latent charge heat will mean that if you get preignition (very easy to do on Ethanol and Methanol) long before your knock sensor picks up "knock". If it ever does. Tuning your engine off your knock sensor is like cooking your food off your smoke alarm.

The knock sensor is pretty sensitive and does a pretty good job of retarding timing for the most part. The added cylinder pressures and temps definitely make it more dangerous when you do get knock but unless you are getting like 20+ counts and holding it for extensive periods which would be bad for either fuel I don't see how it is any worse than the gasoline counterpart. Just as an anecdote to this, I ran my wot tune lean enough so that I got lean misses at 26psi and I still didn't see crap for knock. It ran line garbage and stuttered even with a .24 gap and colder plugs but it didn't knock more than 5-10 counts. Go octane :cool:

[thiazole]

True - I didn't see any real HP benefit beyond upper 11s so I couldn't see the point of going any leaner. I would think that with its big heat capacity and latent heat of vaporization that ethanol is only a risk of preingnition when going very lean.

[thiazole]

Preignition is also why it isn't redundant to use water injection with ethanol. A lot of people say that is pointless because the ethanol cools the intake charge plenty, but I'd bet that on vehicles with water injection it is almost impossible to preignite the intake charge.

[Cloud]

I'm finding it relatively impossible to do it on ethanol. I run into no-ignition problems before I can get into pre-ignition problems :) It does run very hot though when I run it that lean, evidenced by the very light color of my turbine and similar whitness on the plugs. It isn't completely white in color, just a beige, so I know it's still happy just not depositing any carbon.

[v413nc3]

You guys need to learn the difference between detonation and pre-ignition. The knock sensor does NOT pick up on everything and was designed to listen to issues arising from petrol. You start running on something that is very detonation resistant but is prone to pre-ignition and you will have issues tuning off just your knock sensor. You also need to keep an eye on EGT's or you will burn up a valve seat and have issues related to that. Tuning is more than moving sliders and watching knock output.

[thiazole]

I know the difference. I don't think I said anything that indicated I don't. I also previously said and if you don't see knock or excessive combustion temps, then I guess why not?

Edit: I'm pretty sure Brian knows the difference as well.

[v413nc3]

Your knock sensor will not always show pre-ignition issues. It was designed to show detonation issues. Methanol and Ethanol have been used in racing for a long time guys. They figured out years ago that you'll see a lot more pre-ignition with alcohols than detonation. Knowing this you can run your engine to the point of bending your rods before you notice knock, and at that point it may be too late. Your knock sensor is NOT the end all be all of tuning. There are many other things you should take into consideration.

[Cloud]

Ok, how do you bend a rod from pre-ignition? You will deform ring lands and burn valves but I don't see how you are going to bend a rod unless your pre-ignition leads to knock... which will be picked up by the knock sensor.

[Hemicolt]

What about the fuel pump for E85? Thinking of using 1600cc injectors with a big 16g on a stock engine (300ish hp). Will a Walbro 255 be enough? Whats the cut off for a 255?


Im on a 255 hp wally i'm pretty much maxed out now...

[Toybreaker]

Stoopid question from a nOOb to tuning these cars.

Does the ecu "listen" to the knock sensor 24/7, or only around a specific range of crankshaft rotation?
EDIT I ask this because I've seen people say yes, and I've seen other people say no..

I know on some of the other systems that I'm more familiar with, the ecu only "listens" for knock round 'bout when abnormal combustion would be occuring.

If you had true "preignition" going on, and the ecu isn't listening at that point in the crankshaft's rotation, you could drive over your crankshaft, and see smoking hot pissed off bits of your rotating assembly in the rearview mirror...

Long before the ecu ever showed "knock"....

I don't pretend to understand all the little bits and pieces of the whole flame front propagation/central kernal/combustion thang...

But, I do know if your mix is burning early on in the compression stroke, (pre-ignition) the pressures gonna get out of hand quick, an bad sh*t's gonna happen fast. :eek:

...no knock required...

[matthewdesigns]

What about the fuel pump for E85? Thinking of using 1600cc injectors with a big 16g on a stock engine (300ish hp). Will a Walbro 255 be enough? Whats the cut off for a 255?

Here's a few links to fuel pump vs. line pressure ratings. With that info, you can figure out what the theoretical cutoff point is for your pump at (x)psi.

http://www.stealth316.com/2-fuelpumpguide.htm
http://www.vfaq.com/mods/Walbro-specs.html
http://www.roadraceengineering.com/fuelpumpflowrates.htm

And here's a thread I started last year that covers all the math re: injectors, pumps, and line pressure :D

http://codsm.org/forums/showthread.php?t=2174

[thiazole]

Stoopid question from a nOOb to tuning these cars.

Does the ecu "listen" to the knock sensor 24/7, or only around a specific range of crankshaft rotation?
EDIT I ask this because I've seen people say yes, and I've seen other people say no..

I know on some of the other systems that I'm more familiar with, the ecu only "listens" for knock round 'bout when abnormal combustion would be occuring.

If you had true "preignition" going on, and the ecu isn't listening at that point in the crankshaft's rotation, you could drive over your crankshaft, and see smoking hot pissed off bits of your rotating assembly in the rearview mirror...

Long before the ecu ever showed "knock"....

I don't pretend to understand all the little bits and pieces of the whole flame front propagation/central kernal/combustion thang...

But, I do know if your mix is burning early on in the compression stroke, (pre-ignition) the pressures gonna get out of hand quick, an bad sh*t's gonna happen fast. :eek:

...no knock required...

These cars listen for knock ALL the time, which can be unfortunate. Sometimes lifter tick can get so loud that you get major timing retard while you are driving down main street. (and your car will start to puke out and you know what it is). DSMLink allows you to put in parameters where your ECU will ignore knock (ie, below 20% throttle or below 2000rpm are common parameters to have it ignore knock), but otherwise the knock sensor always has a big impact. My point is questioning whether alcohols "really" increase the probability of getting pre-ignition when comparing apples to apples (same wideband reading of a/f ratio, same cylinder temp, etc) or do people who run alcohol tend to push the a/f much closer to stoichiometric causing conditions that are more prone to pre-ignition?

[D Walker]

Typically pre-ignition is the silent killer and does not show up as knock on any sensor. There are exceptions to that rule of course, but its pretty rare.

[thiazole]

I tried to find some source showing that ethanol is more likely to pre-ignite than gasoline, but I really couldn't find anything. The main problem seems to be the fact that most people don't know the difference between pre-ignition and detonation. If anyone has some sources talking about the propensity of ethanol to pre-ignite, post it and I'll have a read. I'm also fairly confident for a lot of reasons that water injection dramatically decrease the probability of pre-ignition, especially with ethanol (keep in mind that water and ethanol hydrogen bond likely making ethanol harder to ignite under any circumstance).

[v413nc3]

The "knock" you'll see when pre-ignition kills your engine will be the rod pushing down on the crank journal the wrong way. Your rod bends a little. And you're already done. No amount of timing being pulled a fuel being added fixes that. There is no small knock curve warning leading to worse stuff in the future. The whole knock theory is that detonation starts small and ramps up so that we can pull timing and add fuel to stop it. Pre-ignition cannot be stopped like that. Things go down hill fast from there. Most people confuse bad rod bearings (spun bearing) for bent rod. It's not my job to tune your car. I wanted to give a heads up to those who are really interested in learning about why tuning purely off a knock sensor is bad with alcohol based fuels. I'll take my soap box and go back to my corner. I'm done in this thread.

[matthewdesigns]

The main problem seems to be the fact that most people don't know the difference between pre-ignition and detonation.

OK, I'll bite. I thought the terms were interchangeable, both relating to the air/fuel mixture igniting before you want it to (one due to timing, and one from excess/latent heat in the cylinder). What's the difference? Or is that the difference?

[thiazole]

Well, I don't know what the exact % of occurances are, but I think Brian is referring to pre-ignition that is triggered by excess detonation which is quite common. I'm not so sure how common pre-ignition without detonation is, but it seems like it would be less common.

[thiazole]

OK, I'll bite. I thought the terms were interchangeable, both relating to the air/fuel mixture igniting before you want it to (one due to timing, and one from excess/latent heat in the cylinder). What's the difference? Or is that the difference?
Nope, pre-ignition is when the new air/fuel mixture spontaneously combusts during the intake stroke. Detonation occurs after ignition is complete (or mostly complete?) which is probably caused by near explosive biproducts of the combustion process (maybe small hydrocarbons or carbon monoxide?). Pre-ignition fights against the compression stroke while detonation pushes in the same direction as the power stroke which is why detonation isn't as bad even though it has a greater "shock" value from being more like an explosion.

[Cloud]

The difference is with detonation you have multiple flame fronts, the spark starts it at the right time but the increase in compression after the initial spark causes other areas to ignite as well making multiple flame fronts and rapidly increasing temperature and pressure and causing a lot of unpleasant harmonics and things of that nature from an uneven burn. The increase in local pressures tends to be extreme and will outright break rings or ring lands and has been known to bend rods as well if bad enough.

Pre-ignition is from the entire mixture igniting before the spark. You can't fix that with retarding timing because the spark has no control over it. Typically pre-ignition is a dangerous cycle. After it happens once it makes the combustion chamber very hot which only makes it pre-ignite even worse then next cycle until everything melts. I have not heard of pre-ignition causing the same kinds of pressures that detonation does so I am not sure why the argument that pre-ignition bends rods has come about. Pre-ignition can and often does lead to detonation however and everything above then applies. What pre-ignition does do is make the engine REALLY hot, combustion without a lot of compression makes it super thermally inefficient and a lot of heat goes into all the engine parts with very, very little going into power. It is easy to soften ring lands or even put a hole in the piston because of the extreme and extra long exposures to high temperatures the internals have to see. The aluminum piston is typically the first to suffer, exhaust valves also tend to get eaten rather quickly as they have the least cooling out of the combustion chamber components and your turbine and exhaust components typically can suffer quickly as well.

I don't know why you don't want to explain your argument for rod bending or why alcohols are more prone to pre-ignition. Are you saying that the pressures from pre-ignition are greater than the pressures from detonation? I don't think that is true. I understand ethanol's burn speed can vary quite a bit more with air fuel ratio than with gasoline but I am not sure why you say specifically that alcohols are prone to pre-ignition and if you have a reason why then I think we would like to hear it still.

[matthewdesigns]

Sorry, CBR600RR.

/hijack

[JackM]

Ok, how do you bend a rod from pre-ignition? You will deform ring lands and burn valves but I don't see how you are going to bend a rod unless your pre-ignition leads to knock... which will be picked up by the knock sensor.

My brother did that. You could see a bend in the area near the big end of his rod. His pistons and valves were fine.

Jack

[thiazole]

Yeah, I agree - heat is probably the biggest thing pre-ignition causes that kills engines. Consider that a turbo running 3:1 pressure ratios can heat 100* air up past 400*. Now imagine if you intake charge ignited and was instantly heated to 800* what would happen to the temp if you then compressed it to 8:1! Things start melting...

[Cloud]

So why do you believe it was pre-ignition that bent the rod Jack? From what I gather the most typical failure from pre-ignition is a big fat hole in the middle of the piston crown where it is thinnest. Do we have good enough piston cooling from oil squirters or something to make this not the typical pre-ignition failure mode?

Also for those who want a very long and detailed account of the differences between pre-ignition and detonation this website has a lot of info:

http://www.streetrodstuff.com/Articles/Engine/Detonation/

[Toybreaker]

I'm leaning my lessons about posting what i know, because I don't know much, (and I can only use expressions like correct propogation of the flame kernal in jest....)

but...


I do know that if you light the mix off early and it's burning and expanding whilst you're trying to compress it, well that's where the pressure to bend rods comes from.

That's all I have to say about that. :)

[thiazole]

I'm leaning my lessons about posting what i know, because I don't know much, (and I can only use expressions like correct propogation of the flame kernal in jest....)
:)



but... I do know that if you light the mix off early and it's burning and expanding whilst you're trying to compress it, well that's where the pressure to bend rods comes from.

That's all I have to say about that. :)

It could happen - it probably depends on a lot of different things, I suppose. Does something melt first or does the pressure grow enough to bend/break things first. Once metal gets close to melting, though, I think the heat just melts its way through and the pressure is released.

[Toybreaker]

I always thought it was about mechanical advantage.

When the rod is operating at a larger angle to the crank, (i.e. the crank at 90* to tdc) then the load path wasn't a straight compression load. Some of the load would be fed into the rod as a bending load, and that's why the rod was more prone to bending when more pressure was applied it earlier in the cycle..

The straighter up the crank was, the less the rod angle would be, the more the force would be a straight compressive load, the less likely the rod would bend, and the more likely you would lift the head/break ring lands etc.

That might be why the detonation failures are more chamber/piston related, and the pre-ignition failures would be more rod/crank related.

I dunno, it's a good question!

[thiazole]

Yeah, that sounds like good logic to me. I didn't even think about the rod angle.

[D Walker]

The coolest thing is when you get pre-ignition on one revolution heating the top of the piston to the point it is pretty much molten, and at the same time heat the piss out of the combustion chamber, leading to actual detonation the next revolution, leading to a nice hole in the top of the piston, and bits of molten alloy in the oil pan... seriously its a good time...

John is absolutely right about the rod/crank failure. Detonation can and will cause rod bearing damage, broken ring lands, etc and is what people are more used to seeing.

[JackM]

So why do you believe it was pre-ignition that bent the rod Jack? From what I gather the most typical failure from pre-ignition is a big fat hole in the middle of the piston crown where it is thinnest. Do we have good enough piston cooling from oil squirters or something to make this not the typical pre-ignition failure mode?

Also for those who want a very long and detailed account of the differences between pre-ignition and detonation this website has a lot of info:

http://www.streetrodstuff.com/Articles/Engine/Detonation/

It's definitely a very good possibility that it was. He was pushing that car far beyond what it was supposed to do with that setup, so pre-ignition was a factor.

Jack

[thiazole]

... I'm still interested in seeing any kind of evidence that ethanol is more prone to pre-ignition than gasoline. It very well might be, but I'd need some evidence because at least anecdotaly, ethanol is harder to ignite .