Choppy dyno, spark plug blowout?
07-03-2015, 01:59 AM
#1
Rennlist Member
Thread Starter
Choppy dyno, spark plug blowout?
I had the car on the dyno, and I am getting really choppy graphs, the guy doing it is very knowledgable but wasn't sure what was causing it. The car was strapped down very tightly to prevent any wheel spin on the rollers, but it is rare for him to have wheel spin (the dyno and rollers are only a month old).
Any thoughts on what could be causing a graph like this? His hunch was maybe spark plug blow out? I plan on checking plugs and gaps in the AM.
This is an M-tune, 17psi, gauge pressure (k27/8), E85, NGK plugs, stock WG with 2.5" exhaust (w/ test pipe).
SAE 12% at mile high elevation.
Any thoughts on what could be causing a graph like this? His hunch was maybe spark plug blow out? I plan on checking plugs and gaps in the AM.
This is an M-tune, 17psi, gauge pressure (k27/8), E85, NGK plugs, stock WG with 2.5" exhaust (w/ test pipe).
SAE 12% at mile high elevation.
Last edited by Xaerran; 07-06-2015 at 01:52 AM.
07-03-2015, 03:49 PM
#3
Rennlist Member
Thread Starter
Thanks Shawn - I happen to have a new (to me) Tial 38mm WG on the workbench. I plan on installing it this week.
Last edited by Xaerran; 07-03-2015 at 04:05 PM.
07-04-2015, 12:23 AM
#5
Rennlist Member
Thread Starter
Choppy dyno, spark plug blowout?
I don't see the tach bounce, but there does seem to be some very slight surging, which seems similar the dyno. It is so slight, it may just be in my head, after seeing the dyno.
07-04-2015, 05:54 PM
#6
Quit Smokin'
Rennlist Member
Rennlist Member
is it just me or is your output low? seems like 260 wheel is not right for that turbo at 17psi....
a guy i tuned with in the past told me that dyno graphs that look like that might be a small timing issue. i took his word for it. we were teching spec miata ecus, and the mule car had wavy traces with the stock ecu, but really smooth curves with the cheater ecu with timing dialed in. the graph you posted isn't super useful without the boost graph. if the boost is ever so slightly fluctuating i would put my money on wastegate fixing it.
a guy i tuned with in the past told me that dyno graphs that look like that might be a small timing issue. i took his word for it. we were teching spec miata ecus, and the mule car had wavy traces with the stock ecu, but really smooth curves with the cheater ecu with timing dialed in. the graph you posted isn't super useful without the boost graph. if the boost is ever so slightly fluctuating i would put my money on wastegate fixing it.
07-04-2015, 10:18 PM
#7
Rennlist Member
Thread Starter
Choppy dyno, spark plug blowout?
Thanks, I will work to get the new exhaust on this week and report back. It is slow going with only jack stands and it being my first exhaust on these cars.
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07-05-2015, 04:43 PM
#11
Drifting
This does look like a boost pressure variance, not a spark plug blow - out. If you had a plug blowing out, you'd likely have a HG issue now. Replacing the stock waste gate is a great first move. I bet your plugs are all in good shape/color.
You're RWH and TQ numbers look great, and the operator wasn't fudging the numbers. You were using a "loaded" Mustang type dyno, and your numbers look fine.
Cut/Paste:
Dyno Confusion FINALLY Cleared Up
Q: It is confusing to the layman. I was a dealership mech. for about 28 years. I just bought two cars from a shop in Ohio. He said one was "450-500". I had it Dyno'd Wed this week. It was 290.4 (RW) 310 torq.(rear wheels). They had a car show in this small town today, I blew two Vett's in the weeds, with 290 HP. I don't understand, this is all confusing. I have decided a long time ago, if you have 900 HP, but you only get 300 to the ground----, then you have a 300 HP. Please let me know your thoughts.
It all depends on the dyno and how it is reading and computing the power / load ratings. There are "inertia" dyno's that give a particular number, and there are "load" dyno's that give an entirely different number. Why do they do this you ask? If you took a typical DynoJet dyno (chassis dyno) and ran a car on it, it would give you a given number based on inertia and the spool-up speed of the drums. If you took that same car and put it on a Mustang Dyno or SuperFlow "load" dyno, you would get a much lower number simply because they are measuring power under different circumstances (under a load).
There is typically a 140 or so HP difference between an inertia dyno and a load dyno. Then you have to take that number and divide it by .85 to get the close approximation of power at the flywheel. Now, some people will argue about the .85 number and say you just need to figure on about a 60HP loss through any typical chassis, so you simply take the rear wheel power number and add about 60 to it and you'll be in the ball park, but most dyno shops will tell you it is an average of 15% - 18% loss through the chassis (on average). Well, .88 to .85 IS 15% - 18% when you are doing the math.
So let's say you have a 450BHP engine (at the flywheel), that would be about the same as 380 RWHP on an inertia chassis dyno. You typically lose about 15% - 18% through the chassis, so 380 divided by .85 = 447HP at the flywheel (basically 450HP). Now, with a "load" chassis dyno, you will typically have about 140 LESS power than you would with a "non-load" (inertia) type of dyno. So take that 380 at the rear wheel and drop that down by 140HP, which comes out to 240 RWHP under a load. So, 240HP under a load 140 variation HP = 380 basic RWHP, now divide that by .85% and you get approximately 447HP at the flywheel.
Your car made 290 RWHP and you blew the doors off of two new Vette's which are quite powerful cars and run fairly easy 12 second quarter mile times. 290 HP isn't enough to run 12's in the quarter mile, not even with a hurrican for a tail wind, so I have to assume that your 290HP was a "loaded" HP reading. If it wasn't a loaded reading, then your engine was only making 341 Flywheel HP (BHP) and that just isn't a number that is very capable of blowing the doors off of two new Vettes, so it had to be a loaded number.
So, 290 RWHP under a load, plus the 140 variation you normally have between inertia dynos and load dynos = 430 non loaded RWHP. Take that and divide it by .85 and you are making in the neighborhood of 505 BHP (at the flywheel).
You're RWH and TQ numbers look great, and the operator wasn't fudging the numbers. You were using a "loaded" Mustang type dyno, and your numbers look fine.
Cut/Paste:
Dyno Confusion FINALLY Cleared Up
Q: It is confusing to the layman. I was a dealership mech. for about 28 years. I just bought two cars from a shop in Ohio. He said one was "450-500". I had it Dyno'd Wed this week. It was 290.4 (RW) 310 torq.(rear wheels). They had a car show in this small town today, I blew two Vett's in the weeds, with 290 HP. I don't understand, this is all confusing. I have decided a long time ago, if you have 900 HP, but you only get 300 to the ground----, then you have a 300 HP. Please let me know your thoughts.
It all depends on the dyno and how it is reading and computing the power / load ratings. There are "inertia" dyno's that give a particular number, and there are "load" dyno's that give an entirely different number. Why do they do this you ask? If you took a typical DynoJet dyno (chassis dyno) and ran a car on it, it would give you a given number based on inertia and the spool-up speed of the drums. If you took that same car and put it on a Mustang Dyno or SuperFlow "load" dyno, you would get a much lower number simply because they are measuring power under different circumstances (under a load).
There is typically a 140 or so HP difference between an inertia dyno and a load dyno. Then you have to take that number and divide it by .85 to get the close approximation of power at the flywheel. Now, some people will argue about the .85 number and say you just need to figure on about a 60HP loss through any typical chassis, so you simply take the rear wheel power number and add about 60 to it and you'll be in the ball park, but most dyno shops will tell you it is an average of 15% - 18% loss through the chassis (on average). Well, .88 to .85 IS 15% - 18% when you are doing the math.
So let's say you have a 450BHP engine (at the flywheel), that would be about the same as 380 RWHP on an inertia chassis dyno. You typically lose about 15% - 18% through the chassis, so 380 divided by .85 = 447HP at the flywheel (basically 450HP). Now, with a "load" chassis dyno, you will typically have about 140 LESS power than you would with a "non-load" (inertia) type of dyno. So take that 380 at the rear wheel and drop that down by 140HP, which comes out to 240 RWHP under a load. So, 240HP under a load 140 variation HP = 380 basic RWHP, now divide that by .85% and you get approximately 447HP at the flywheel.
Your car made 290 RWHP and you blew the doors off of two new Vette's which are quite powerful cars and run fairly easy 12 second quarter mile times. 290 HP isn't enough to run 12's in the quarter mile, not even with a hurrican for a tail wind, so I have to assume that your 290HP was a "loaded" HP reading. If it wasn't a loaded reading, then your engine was only making 341 Flywheel HP (BHP) and that just isn't a number that is very capable of blowing the doors off of two new Vettes, so it had to be a loaded number.
So, 290 RWHP under a load, plus the 140 variation you normally have between inertia dynos and load dynos = 430 non loaded RWHP. Take that and divide it by .85 and you are making in the neighborhood of 505 BHP (at the flywheel).
07-05-2015, 09:09 PM
#12
Three Wheelin'
This does look like a boost pressure variance, not a spark plug blow - out. If you had a plug blowing out, you'd likely have a HG issue now. Replacing the stock waste gate is a great first move. I bet your plugs are all in good shape/color.
You're RWH and TQ numbers look great, and the operator wasn't fudging the numbers. You were using a "loaded" Mustang type dyno, and your numbers look fine.
Cut/Paste:
Dyno Confusion FINALLY Cleared Up
Q: It is confusing to the layman. I was a dealership mech. for about 28 years. I just bought two cars from a shop in Ohio. He said one was "450-500". I had it Dyno'd Wed this week. It was 290.4 (RW) 310 torq.(rear wheels). They had a car show in this small town today, I blew two Vett's in the weeds, with 290 HP. I don't understand, this is all confusing. I have decided a long time ago, if you have 900 HP, but you only get 300 to the ground----, then you have a 300 HP. Please let me know your thoughts.
It all depends on the dyno and how it is reading and computing the power / load ratings. There are "inertia" dyno's that give a particular number, and there are "load" dyno's that give an entirely different number. Why do they do this you ask? If you took a typical DynoJet dyno (chassis dyno) and ran a car on it, it would give you a given number based on inertia and the spool-up speed of the drums. If you took that same car and put it on a Mustang Dyno or SuperFlow "load" dyno, you would get a much lower number simply because they are measuring power under different circumstances (under a load).
There is typically a 140 or so HP difference between an inertia dyno and a load dyno. Then you have to take that number and divide it by .85 to get the close approximation of power at the flywheel. Now, some people will argue about the .85 number and say you just need to figure on about a 60HP loss through any typical chassis, so you simply take the rear wheel power number and add about 60 to it and you'll be in the ball park, but most dyno shops will tell you it is an average of 15% - 18% loss through the chassis (on average). Well, .88 to .85 IS 15% - 18% when you are doing the math.
So let's say you have a 450BHP engine (at the flywheel), that would be about the same as 380 RWHP on an inertia chassis dyno. You typically lose about 15% - 18% through the chassis, so 380 divided by .85 = 447HP at the flywheel (basically 450HP). Now, with a "load" chassis dyno, you will typically have about 140 LESS power than you would with a "non-load" (inertia) type of dyno. So take that 380 at the rear wheel and drop that down by 140HP, which comes out to 240 RWHP under a load. So, 240HP under a load 140 variation HP = 380 basic RWHP, now divide that by .85% and you get approximately 447HP at the flywheel.
Your car made 290 RWHP and you blew the doors off of two new Vette's which are quite powerful cars and run fairly easy 12 second quarter mile times. 290 HP isn't enough to run 12's in the quarter mile, not even with a hurrican for a tail wind, so I have to assume that your 290HP was a "loaded" HP reading. If it wasn't a loaded reading, then your engine was only making 341 Flywheel HP (BHP) and that just isn't a number that is very capable of blowing the doors off of two new Vettes, so it had to be a loaded number.
So, 290 RWHP under a load, plus the 140 variation you normally have between inertia dynos and load dynos = 430 non loaded RWHP. Take that and divide it by .85 and you are making in the neighborhood of 505 BHP (at the flywheel).
You're RWH and TQ numbers look great, and the operator wasn't fudging the numbers. You were using a "loaded" Mustang type dyno, and your numbers look fine.
Cut/Paste:
Dyno Confusion FINALLY Cleared Up
Q: It is confusing to the layman. I was a dealership mech. for about 28 years. I just bought two cars from a shop in Ohio. He said one was "450-500". I had it Dyno'd Wed this week. It was 290.4 (RW) 310 torq.(rear wheels). They had a car show in this small town today, I blew two Vett's in the weeds, with 290 HP. I don't understand, this is all confusing. I have decided a long time ago, if you have 900 HP, but you only get 300 to the ground----, then you have a 300 HP. Please let me know your thoughts.
It all depends on the dyno and how it is reading and computing the power / load ratings. There are "inertia" dyno's that give a particular number, and there are "load" dyno's that give an entirely different number. Why do they do this you ask? If you took a typical DynoJet dyno (chassis dyno) and ran a car on it, it would give you a given number based on inertia and the spool-up speed of the drums. If you took that same car and put it on a Mustang Dyno or SuperFlow "load" dyno, you would get a much lower number simply because they are measuring power under different circumstances (under a load).
There is typically a 140 or so HP difference between an inertia dyno and a load dyno. Then you have to take that number and divide it by .85 to get the close approximation of power at the flywheel. Now, some people will argue about the .85 number and say you just need to figure on about a 60HP loss through any typical chassis, so you simply take the rear wheel power number and add about 60 to it and you'll be in the ball park, but most dyno shops will tell you it is an average of 15% - 18% loss through the chassis (on average). Well, .88 to .85 IS 15% - 18% when you are doing the math.
So let's say you have a 450BHP engine (at the flywheel), that would be about the same as 380 RWHP on an inertia chassis dyno. You typically lose about 15% - 18% through the chassis, so 380 divided by .85 = 447HP at the flywheel (basically 450HP). Now, with a "load" chassis dyno, you will typically have about 140 LESS power than you would with a "non-load" (inertia) type of dyno. So take that 380 at the rear wheel and drop that down by 140HP, which comes out to 240 RWHP under a load. So, 240HP under a load 140 variation HP = 380 basic RWHP, now divide that by .85% and you get approximately 447HP at the flywheel.
Your car made 290 RWHP and you blew the doors off of two new Vette's which are quite powerful cars and run fairly easy 12 second quarter mile times. 290 HP isn't enough to run 12's in the quarter mile, not even with a hurrican for a tail wind, so I have to assume that your 290HP was a "loaded" HP reading. If it wasn't a loaded reading, then your engine was only making 341 Flywheel HP (BHP) and that just isn't a number that is very capable of blowing the doors off of two new Vettes, so it had to be a loaded number.
So, 290 RWHP under a load, plus the 140 variation you normally have between inertia dynos and load dynos = 430 non loaded RWHP. Take that and divide it by .85 and you are making in the neighborhood of 505 BHP (at the flywheel).
Dynos are tuning tools first and foremost, not absolute measures unless intended and set up as such.
Like my engine-builder friend says, "Anyone can make horsepower - just lie".
True comparison takes more effort...
07-05-2015, 09:30 PM
#13
Drifting
Love that explanation. Add 140 BHP "just because" (no rational physics-based explanation), then multiply by a magic number to give you the number you wanted in the first place...
Dynos are tuning tools first and foremost, not absolute measures unless intended and set up as such.
Like my engine-builder friend says, "Anyone can make horsepower - just lie".
True comparison takes more effort...
Dynos are tuning tools first and foremost, not absolute measures unless intended and set up as such.
Like my engine-builder friend says, "Anyone can make horsepower - just lie".
True comparison takes more effort...
Not my numbers or math, hence the "CUT - PASTE". The differences between "load" and "inertia" dyno numbers are real. I've got plenty of dyno graphs showing this cut/paste from my personal cars using both to back up the simple math.
Know, torque wins races, HP sells cars. I use dyno's to tune, and can't do this with inertia type dyno setups, as you can only use them for WOT numbers, also you can't use your brakes on a "loaded" dyno, but can replicate real world loaded readings, and adjust your timing/fuel mandates on the fly. Just understand the "loaded" dynos are called, "Heart Breakers."
HP is just a measurement from TQ at a stated RPM. Conversion of inertia - twist from any power plant driving something.
The most reliable way to measure the power from an engine is an engine dyno, not the load or inertia wheel setups we use for tuning - bragging.
Dyno's don't lie, operators do.
07-05-2015, 09:34 PM
#14
Drifting
Love that explanation. Add 140 BHP "just because" (no rational physics-based explanation), then multiply by a magic number to give you the number you wanted in the first place...
Dynos are tuning tools first and foremost, not absolute measures unless intended and set up as such.
Like my engine-builder friend says, "Anyone can make horsepower - just lie".
True comparison takes more effort...
Dynos are tuning tools first and foremost, not absolute measures unless intended and set up as such.
Like my engine-builder friend says, "Anyone can make horsepower - just lie".
True comparison takes more effort...
07-05-2015, 11:28 PM
#15
Three Wheelin'
Hi George, wasn't getting at you - just the article. My apologies.
Didn't mean to derail this thread, particularly since the dyno info is being used to diagnose, not brag.
(I designed a hybrid inertia/loaded dyno 20 years ago, only 250kW steady-state but the inertia added enough capability for higher power on various driving cycles)
Cheers,
Mike
Didn't mean to derail this thread, particularly since the dyno info is being used to diagnose, not brag.
(I designed a hybrid inertia/loaded dyno 20 years ago, only 250kW steady-state but the inertia added enough capability for higher power on various driving cycles)
Cheers,
Mike