Burn Down - Fuel - Pipes - EGT Information

[WildMax]

Hello Fellow Vmax4 riders,

Earlier this month I posted my busted piston topic (see the “WildMax Down” post for several photos of the engine). Anyway, I thought that I would follow up on that post as well as share some information on several other topics that have been posted since then that relate to this issue.

I have had a few conversations with Pat Hauck regarding this. He modified my total top end prior to the busted piston and had me send him my “pieces” so he could look them over. I’ll just relay some info in a Q&A format, paraphrased to what Pat indicated.

I’m not going to argue that this is the ultimate word on these topics but just wanted to pass on the answers Pat gave me.

Q – From my parts, can you tell what went wrong and caused the busted piston?
A – Yes, it looks like you were running too lean.

Q – All things staying the same (sled, elevation, temp, riding style, etc.) with the only changes being the engine modifications you did, (heads, cylinders, pistons, gaskets) what difference in jetting would you advise?
A – Probably go 2 steps richer. Each step being 2.5 on the jet scale would mean if you were at 135 mains, now go to 140’s.
(WildMax comment – from this advise, I was about 2 steps too lean – not very detectable from the plugs and piston wash but ...)

Q – There has been talk of “bad fuel” issues and how it can cause this. Have you seen much problem with bad fuel come through your shop?
A – Not really. Most fuel problems seem to come from guys using 87 or lower octane. If you run 91 there is seldom a problem.

Q – With the engine modifications you did for me, is it necessary to use a fuel additive to boost octane?
A – No, you should be fine on 91 octane straight from the pump. Your modifications should give you about an additional 16 horsepower which you should notice at low and mid range throttle. Extra octane will not make much of a difference with your engine as it was built for trail performance, not the race track.

Q – Regarding aftermarket pipes, PSI, Hauck, Bender or whatever ones are put on, if the engine is not jetted for optimum burn with those pipes, as per the pipe makers recommendations, do the pipes perform as well as the stock exhaust? i.e. With quad pipes, if I want to run a few steps rich on the jetting to be safe am I making any extra horsepower or am I better off to just leave the stock exhaust on?
A – Yes and no. It depends on what machine you are adding pipes to, SRX, Viper, VMax, etc. Taking the vx800 engine, PSI says about 22 horsepower is added with their pipes. That would be at optimum burn. If you increase the jet size a couple of steps to be on the safe side you would not see the full performance of those pipes but more like an 18 horsepower increase. That is still better than stock.

Q – Is the same thing true for modifications done to the engine – any gained performance when jetting a little rich versus jetting on the border line?
A – Yes. Jetting on the ‘line’ might get you the full potential from the mods but you will still see good performance results when jetting safe.

Q – The cost of a burn down would easily buy an EGT set up. What’s a good exhaust gas temp to be at on a vx800?
A – A lot of guys with EGT gauges on their sleds burn down, too. 1250 degrees is ok. 1200 would be pretty safe.

Q – If I was to install sensors on two pipes, what are the best choices, 1 and 3?
A – Numbers 1 and 3 seem to have the most problems so that would probably be ok.

[SRV540]

HMMM straight from the horses mouth......intresting answers he gave you WildMax, are you running EGT's? I am not sure I would feel safe on just monitoring 2 pipes out of 4 if thats what you mean? I just picked up 4 probes and wires and am going to build my own quad digital EGT (DPM) guage......seen alot of homeade triple egt's on ebay.....thanks for the interesting post dude!

[yammiman]

100's of post's and a excellent member gone over this - hope someone learned something!

[Chevy2]

The one thing i learned is to jet up when using pump gas, and you can still make good power. :sled:

[yammiman]

Yeah, and stock jetting wouldn't make much just like it has been said!

[Chevy2]

I wouldn't worry about 2-4 hp on a trail sled. You will never notice the difference unless its on a dyno. :schild27:

[Skinner]

100's of post's and a excellent member gone over this - hope someone learned something!

DIDO
My thoughts exactly
Great info Wildmax

Skinner

[vmax4rules]

WildMax thanks for sharing the info!

[VMAX80096]

I run digitron 4 window egts and run psi quads with internal silencers, airbox gutted and opened up with temps between 1200 and 1250 with premium gas and make 173hp, without ever having a burn down

[WildMax]

are you running EGT's? I am not sure I would feel safe on just monitoring 2 pipes out of 4 if thats what you mean?

No, I do not have an EGT set up. With the cost of having a cylinder rebuilt, I just brought it up in the conversations and we talked about them. What Pat was pointing out to me was that even with EGT, engine damage can happen pretty fast if the fuel leans out. Fast enough that guys with them can get into trouble before they notice the readout.

Thinking about this for my riding and lack of great eyesight, what would be cool would be an EGT display similar to the HalTech air/fuel ratio meters that I put on my turbo projects. This is a series of different colored led’s in lieu of numbers or dials – and large enough for me to see.

[SRV540]

yeah that would be easier to notice, I have a hard time even looking at the speedo or tach for very long, unless I am putting around at 10mph.......not!

[racer7x]

The Digatron EGT's have warning lights that you can set to your desired temps. That way you dont have to look at the #'s just watch for the warning light. SIMPLE

[Skinner]

No, I do not have an EGT set up. With the cost of having a cylinder rebuilt, I just brought it up in the conversations and we talked about them. What Pat was pointing out to me was that even with EGT, engine damage can happen pretty fast if the fuel leans out. Fast enough that guys with them can get into trouble before they notice the readout.

Thinking about this for my riding and lack of great eyesight, what would be cool would be an EGT display similar to the HalTech air/fuel ratio meters that I put on my turbo projects. This is a series of different colored led’s in lieu of numbers or dials – and large enough for me to see.

You and Pat are correct. Go back and read Toydocs post on EGT's and take the time to try and really understand it. The temp in the combustion chamber may be toatally different than what the probe reads in the pipe. Again we are back to variables. Different fuels burn, atomize and explode at different rates, and if you read Toydocs post, he asked why a motor would burn down with the exhaust temps at 1050 if I remember correctly. Another thing I see that has not been much of a topic here, and I think is under recognized is "IGNITION TIMING". You also need to understand what Pat is saying, there is a difference between a dragsled and a trailsled. You don't need the optimum hp gains from the dyno sheets and all the other wonderful things they tell you because the variables are controlled. The trail guys are at the mercy of the pump which are inconsistancies. Jet safe, trail ride and don't worry about the max 22 hp out of a set of PSI's.
Most trail riders don't carry a scope to check piston wash every five miles. You bet they do it after a run in the race trailer

Skinner

[racer7x]

Here is an article sent in about fuel......... Very good reading...

BAD GASOLINE
One of the most frequently encountered problems this season is the issue of “bad gas”. While not involving flatulence, it just as big a problem.
We have had more fuel-related problems ranging from poor starting, hesitation, etc. to just plain “quit and won’t restart” this year than in any of the past 25 years we have been here.
A further explanation of the two different areas of concern with gasoline may be in order for those who wish to pursue it.
1.) OCTANE
This is the resistance to detonation the gasoline offers. The most common grades of gasoline are: REGULAR at 87 Octane; MID-GRADE at 87-90 Octane; PREMIUM at generally 93 Octane. Other custom-built racing gasolines can offer up to 125 Octane. Octane is an indicator of the speed at which the gasoline burns in the engine.
The higher the octane, the slower the speed of the burn; the lower the octane the faster the burn. If the burn is too fast, uncontrolled combustion can occur. This most often is heard as “pinging” and is commonly referred to as detonation. This is because instead of burning through top dead center of the combustion stroke, the entire charge is ignited too early and explodes in the chamber and acts as a bomb. Conversely, if the speed of the burn is too slow, it continues after the useful work can be done in the motor and manifests itself as poor throttle response, reduced power output and increased emissions and fuel consumption. An engineering fact: THE MOST HORSEPOWER IS MADE AT THE THRESHOLD OF DETONATION. We have often gained horsepower on the dyno and felt improved starting and driveability going from Premium grade gas to Regular. This change was recently quantified in a customer’s Ducati M900 by reducing the cranking time to start-up from 15 to 3 revolutions, although part of the improvement is explained below.
The multi-valve combustion chambers and their reduced flame front propagation distances in the modern engines virtually eliminates the need for high-octane gasoline.
2.) COMBUSTIBILITY
This is the ability of the gas to burn. As mentioned above, gasoline needs to burn to be of any value in the motor. Modern gasoline has been subject to formulation restrictions that now make it able to sit only 4 to 6 weeks after manufacture before its usefulness as a fuel is compromised due to reduced combustibility. This is basically a separate issue from the speed of the burn as controlled by octane.
The biggest issue is the fact that the “volatiles” in this new formulation evaporate very quickly.
The reason these “volatiles” are so important is that they are the part of the gasoline that affects starting and throttle response. That is why you can often feel the difference between individual tanks of gas when it comes to starting, cold running and acceleration at lower rpms. The evaporation of these volatiles leaves a thicker, more viscous residue that becomes difficult for the carburetor to break up into combustible droplets. This sludge will adhere to the intake runner walls or goo its way into the combustion chamber.
The poor burning characteristics can be seen in the accompanying photo.

This difference becomes more pronounced with carbureted bikes using a hemi-style engine design (Harleys, Viragos, BMW, Ducati, etc.) as opposed to 4-valve and/or fuel injected motors.
One of the recurring themes in these problems has been the use of Premium gasoline.
There are no 4-valves bikes made in the last 20 years that need premium gasoline for normal street use. Very few of the 2-valve bikes need it either. One of the problems with premium is the fact that it is not used as much and sits in the ground much longer than the other grades, with the attending evaporation of the volatiles present at manufacture. This coupled with the more efficient combustion chambers used today makes the problem even worse. A second issue is the different ways used to achieve that higher octane. Each company has a different formulation, and with the high horsepower to displacement ratios of the newer bikes, tuning for this can be an issue.
A good rule of thumb is if the bike doesn’t ping and runs acceptably with regular, DON’T use Premium. Regular is sold faster, is fresher and will generally start easier and have better throttle response than the higher octane gasolines. Not nearly as many cars use premium as they can compensate for the lower octane of regular with built-in detonation sensors to compensate for the octane, thus reducing the amount of premium sold. Most underground tanks hold in excess of 4,000 gallons of gas, so with primarily motorcyclists buying it three or four gallons at a time, it will be there quite awhile. Also as the level in the tank drops it affords more opportunity for the volatiles to evaporate. It doesn’t matter what the owner’s manual or your friends say. We have often GAINED horsepower on the dyno when we took away octane.
We have had to make arrangements to properly dispose of all the gas that makes a bike run terribly, but works fine in a car or truck. So try a tankful or two of regular and see how the starting and performance changes. If the bike is unhappy, go back to what you were using before, but bear in mind the information here and be ready to switch if things change.
A good way to avoid problems such as this is to be certain you buy gasoline at a name-brand station. The neighborhood convenience store buys gas from a broker, so you have no idea what it is. That gasoline is purchased by price, not specification. Also do not use ethanol-dosed gasoline, as it can be very reactive with the metal used in carburetor bodies. Brand name stations have much more control over the product they sell. We use Amoco Regular as our baseline gasoline in the shop due to convenience, but occasionally make the trip to Shell for what a lot of our customers have said gave the best results in their bikes, especially the twins. Sealed containers of VP gasoline (some costing $42 per gallon) is another alternative, although cost prohibitive.
Remember- always buy brand name fuels to reduce the potential entertainment that accompanies poor quality gasoline.

[WildMax]

BAD GASOLINE...One of the recurring themes in these problems has been the use of Premium gasoline....One of the problems with premium is the fact that it is not used as much and sits in the ground much longer than the other grades, with the attending evaporation of the volatiles present at manufacture. This coupled with the more efficient combustion chambers used today makes the problem even worse.
...Regular is sold faster, is fresher and will generally start easier and have better throttle response than the higher octane gasolines....Most underground tanks hold in excess of 4,000 gallons of gas, so with primarily motorcyclists buying it three or four gallons at a time, it will be there quite awhile. Also as the level in the tank drops it affords more opportunity for the volatiles to evaporate.
A good way to avoid problems such as this is to be certain you buy gasoline at a name-brand station. Remember- always buy brand name fuels to reduce the potential entertainment that accompanies poor quality gasoline.


Yes, Racer! Good article. This could have been a major contributor to my piston break.

RIDERS TAKE NOTE and BE YE WARNED -

I checked my plugs and piston wash every 1/2 hour and found no evidence of leaning - not as rich as I used to be before the rebuild but probably still on the safe side of the line. I had 250 miles on the new engine using 91 octane from the same 2 places that I always buy from.

Since we finally had enough snow, we took a different route and encountered a roadside station that offered 94 octane at an attractive price. I filled the VX800. Now, this station is one that I have never used before and may have had this 94 octane in their pump for who knows how long as we have not had the snow for snowmobiles to get over there for 3 years. They were on a paved highway a few miles outside of Deadwood but by no means a regular fuel stop for cars or sleds - more of a tourist type cafe/fuel/gift store. I probably put in 7 gallons.

We rode about 20 miles at trail speeds then, finding a nice flat stretch of open road, decided to compare the performance of the new engine to the SRX. It was on the second WOT run that the engine failed.

So - maybe "old" fuel from the station combined with border line jetting did me in. I think if I have to buy fuel from an unknown again, I will just get enough to get me to my trailer and take it easy getting there.

AND RIGHT NOW I am going out to the VX800 (which I just put back together yesterday - sounds beautiful) and remove that remaining gas from the tank.

[yammiman]

Optumum jetting + quality fuel = maximum horsepower - pretty simple equation that holds true for any internal combustion engine that is being built for performance - I guess that is why you don't see Nascar's and top fuel dragsters running on pump gas! - how much more can this topic be beat? LOL

[Chevy2]

Optumum jetting + quality fuel = maximum horsepower - pretty simple equation that holds true for any internal combustion engine that is being built for performance - I guess that is why you don't see Nascar's and top fuel dragsters running on pump gas! - how much more can this topic be beat? LOL


Nascar and top fuel don't use pump gas because of the increase in compression ratio. If you take two identical 8.5:1 compresion small block chevys engines, one on 87 octane, and the other on 114 octane race gas, the 87 octane motor will make more power all day long. High octane gas is NOT whats makes power, its to slow down the burn.

[SRV540]

But you can compare the average v4 with quads and a few other mods to the full blow race sleds either, I dont think this topic is being beat, there are people out here that like to gather as much info as possible, is that what these boards are for?? or you just dont like talking or hearing about pipes and bad gas...speaking of bad gas.....lol

[Skinner]

Optumum jetting + quality fuel = maximum horsepower - pretty simple equation that holds true for any internal combustion engine that is being built for performance - I guess that is why you don't see Nascar's and top fuel dragsters running on pump gas! - how much more can this topic be beat? LOL

I think this topic could be beat for eternity because there is so much to it. But its not just the fuel, its compression, timing, carbueration, temp, humidty, etc, etc, etc,. What is the mix of components used? If all race motors, trail motors, lawn mowers, weed whackers and anything else with a piston were the same, they would all perform the same.
No sense in: "lining them up"

[jeff242424]

now may i pose a ??????. this article is written about bikes, and bikes are ridden in the summer time, does cold weather affect the fireing of a cold motor??? and assuming they are talking about 4 strokes, does it affect 2 strokes the same way and lastly, i should try 87 octane(reg) fuel if i get heasitation or pinging???????? i am not an mototr guru but this is what i got out of this article. it is a great article dean, just some ?????? for me. thanks guys.

Rick

[Skinner]

Rick

The ambient air temperature is a HUGE factor in jetting a 2 stroke

[yammiman]

It is a huge factor in jetting any engine - why do you think guys take a weather station and a box of jets to the dragstrip - on the high end race cars (funny cars, fuel dragsters, Indy cars) that is all monitored and controled via computer - but in the final analysis it is all about air and fuel - the more air combined with the right amount of quality fuel (quality does not equal octane) creates the greatest amount of power - when I say quality fuel I mean fuel that is suppose to be 91 octane is actually in fact 91 octane - there is no guarantee of quality fuel out of a Speedway pump! - it is also why everything (including snowmobiles) are going to EFI - it is the weather station and jet changing done for you electronically!

[WildMax]

I had a '94 Wildcat 700 EFI a few years ago and thought it was great. Then Cat (and others) dropped the EFI and went back to carbs but now I see more sleds are offering EFI. I suppose for racing folks, the carbs give them better control but for the average trail rider like me, it was pretty fool proof.

With that Wildcat, it seemed like it was pretty fast and responsive (how it compares to my SRX I don't know but the Wildcat top end was right up there) and riding hard I would never get below 14 mpg and many times it would average 17 mpg. Just amazed me because I also had a carbed ZR which got like 7 mpg. I don't know why Cat dropped the EFI after that - at least until recently.

[AL P]

okay heres my latest "theory"
lets suppose i decide i want the full gain out of my pipes so I decide to run a race fuel mix. okay, then I jet down to a perfect burn temp. because I`m running a race fuel "mix", well, what am i "mixing" my race fuel with? pump premium right?
well what if I get some "bad/stale" pump premium and i mix that with my race gas, would`nt i still have a problem? or does race fuel mean that its imposible to burn down?
My point is, yeah, you may get some bad gas from time to time at the pump, but how would running a race fuel "mix" be any safer? if you were jetting down and running right oin the edge? would`nt putting some bad pump premium in with your race fuel still cause a problem?
so unless you KNOW your getting "good" pump premium, would`nt either case be just as risky with the only differance bieng you would gain a few more HP running a race fuel mix?

[3ft]

I think that all would agree that "bad" gas no matter...is not going to be a good thing. My thoughts on this is that their is NO totally safe way go go about this. It all comes down to the desired octain you need to run with out melting down....The old saying....."It never ran better, and them it let go" I have heard that alot. You will yeild the most power and the sled will feel like an animal right up to the time it lets go. Now.....what animal are you looking for. personally I beleive I can run Quads on pump gas, netting a decent gain safely ...Not seeing the full potential. I'm ok with that. I trail ride and have to have the safety margin factored in. If I can semi-safely see 12-15 hp gain (not the 22 specified) I am one happy camper! I call it good enough and go ride.

[yammiman]

ALP - let me address your theory - lets say your sled is set up to run on 91 octane fuel - lets say you mix it with 94 octane race fuel - now you have 92.5 octane fuel - now lets say you get some fuel that is suppose to be 91 octane but is only 89 octane - when you mix it with the 94 octane, you still have 91.5 octane - I think some guys think "race fuel" mean high octane - you can buy race fuel in an assortment of octanes - the difference is that it is what it is suppose to be - 94 octane is 94 octane and it is made to higher standards so it does not break down and loose its octane rating - the pump gas of today starts to breakdown after 1 to 2 weeks - so that little gas station out in BFE that has a 1000 gallon tank but only pumps 50 gallons a week probably has some pretty scary fuel - but if you mixed it with the right octane race fuel, it would be okay

[micultra]

Al P. I'm no Expert... But bad gas? I'm sure there are lower than advertised octane...but bad gas? The race gas/ pump mix should be premium pump. Why get low octane and spend $$ on race fuel to raise your octane if you buy low octane pump? Doesn't make sence.Piping your sled,jetting your sled, any mod's period are risky. But if done properly you can get major profits from it. It all depends on how you ride,racing...Do it! Trail up to you... I would... But iof your uncomfortable with the chance....I'm looking for quad pipes... Concider selling them? It boils down to your comfort ZONE where are your happy? Performance? reliability? a little of both?

I do believe race/premium mix is NOT needed for stock sleds unless these's an octane switch.(timing related) Now stock running pipes or jetting...another story. Only race/premium if you modded your compression,porting,timing,ect.ect.
Just my thought's
Charles

[AL P]

I`m not the slightest bit worried about running my pipes.
The problem with the race fuel mix theory is, how do you know ecactly what gas your getting at that gas station in bfe? how do you know how much race fuel to mix in to get the correct rating?,,,,,You dont. the point is, its just a geussing game. so I dont see how running a race fuel mix, is going to allow you to jet right on the edge without posibley having a problem due to some gas sations gas bieng bad (as in stale, incorrect rating, ect.)

micultra. refer to post 14 of this thread, and you`ll see what i meant by "bad gas"
i was`nt talking about getting 87 octane rated gas at the pump.

[micultra]

My bust... just sharing my thoughts

I'm sure there is a way to Know exactly what gas you get from the pump...i.e a testor of sorts. Perhaps we should be looking for that vrs. guessing what gas to get?

[yammiman]

ALP - It all boils down to what you want to do with your sled - if you want to do some racing, run the jetting on the edge with a 50/50 blend of pump premium and 100 octane - if you are going to trail ride, just jet it safe and take whatever power increase you get - I know how we could make a potfull of money - invent an aftermarket EFI for older sleds and/or a DCS like what was on the 02 SRX's that could be put on older sleds - we would be in jetting/burndown heaven!
One last thought to confuse this more - think of octane as jetting - the more octane, the richer you are - the less octane, the leaner you are - that is why a motor designed to run on 87 octane fuel actually slows down when you run it on 110 octane - it is the same as richening the mixture.

[micultra]

Yammieman nice point..Eye opener
THANKS
Charles

[AL P]

ALP - It all boils down to what you want to do with your sled - if you want to do some racing, run the jetting on the edge with a 50/50 blend of pump premium and 100 octane - if you are going to trail ride, just jet it safe and take whatever power increase you get - .

this exactly what I`ve been trying to say for about a week.
yes you should be able to run pump premium with psi quads and still get an increase in HP, yes, you would likely get more of an increase running a race fuel mix. but it is not writen in stone that you HAVE to run race fuel to see an increase in HP running psi pipes

My only disagreement on any of the gas issue, was when I was bieng told there would be NO gain what so ever, and if i ran my pipes on pump premium, i would be showing my pistons on vmax4.com. I just did`nt/dont agree with that.
Were all pretty much saying the same thing, just differant ways of saying it.

todays gas sucks, so ya have to jet acordingly,

if you run pump premium, you wont get the full increase of HP intended with these pipes due to having to jet so big, but you will still see a decent gain, and it can be done "somewhat" safely.

wether or not you run a race fuel mix, or pump premium, depends on your mods(compression), and what your doing with your vmax4 ie racing, trail rideing ect.

[yammiman]

I say we put this topic to bed and let her sleep!