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V8 vs V6 by treborerellim
Started on: 12-20-2021 08:28 PM
Replies: 65 (1168 views)
Last post by: Skybax on 01-18-2022 07:20 PM
treborerellim
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Report this Post12-20-2021 08:28 PM Click Here to See the Profile for treborerellimClick Here to Email treborerellimSend a Private Message to treborerellimEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have 2 Fieros a formula with a Cadillac V8 and 4-speed automatic. I also have a 87 GT V6 5-speed. The funny thing is the V8 can't keep up with the six-cylinder. The V8 is a dog. The transmission sometimes starts in low gear sometimes it doesn't will not kickdown at any speed. I had the wiring harness made by a forum member and the e c m reprogrammed by another member. I am very disappointed in the way it runs. I have another Cadillac engine sitting in the garage that I was going to put in the five speed. But after all the problems I've had with the formula V8 if I do I'll go carbureted less aggravation. I don't know where to begin to fix these problems. I'm an old carburetor and distributor guy. My first car was a 55 Chevy coupe 3 speed that I bought in 1965. I do like the way the V8 cruises down the highway. I wish it had a little more Giddy Up and Go.

Bob
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Report this Post12-20-2021 08:32 PM Click Here to See the Profile for RWDPLZClick Here to visit RWDPLZ's HomePageSend a Private Message to RWDPLZEdit/Delete MessageReply w/QuoteDirect Link to This Post
At this point if you're gonna put a V8 in a Fiero, LSX.
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Report this Post12-20-2021 09:27 PM Click Here to See the Profile for cvxjetClick Here to Email cvxjetSend a Private Message to cvxjetEdit/Delete MessageReply w/QuoteDirect Link to This Post
Two engines I think would be good for swap; The LS4 which is the only TRANSVERSE mount V8 (310 hp) the other would be the new 4.3 V6- They completely redid it using tech from the LT V8s....It is actually only 300 lbs, which is 70 lbs lighter than the 2.8 V6....It has 290 HP.....

I actually have a carb V8 (460) in my jetboat.....Did not do any tuning for 10 years (Edelbrock/Carter carb)....Had to clean the carb two years ago but still no tuning (And the plugs look great)
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Dennis LaGrua
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Report this Post12-20-2021 09:51 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The Cadillac 4.9L engine is certainly not a high performance engine but I would not call it a dog. With 275 ft lbs of torque thats a significant increase over the 2.8L. If your 4.9L Fiero cannot keep up with the 2.8L V6 Fiero then something is either wrong with the engine, the installation or the programming/ wiring. The 2.8L has been road tested to be a 16 second car in the 1/4 mile, the 4.9L Fiero working properly should get you into the low 14's.
First thing is to scan the ECM to see if it is going into closed loop and to determine if everything is working correctly. If you are operating in "limp home mode" the engine will be very sluggish. If you are looking for an upgrade in performance, its an economical choice for more power, but if you desire lightning fast performance its not the V8 to have. Then move on to the other suggestions here.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
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87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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Report this Post12-20-2021 09:57 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
The Cadillac High Technology V8 should feel like a rocketship compared to the stock Fiero V6. There must be some issue with the engine, not necessarily mechanical, possibly related to the computer.

I don't know if your car has the same problem, but you may want to read through the recent thread:
https://www.fiero.nl/forum/Forum1/HTML/099807.html
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Report this Post12-20-2021 10:14 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by treborerellim:

Cadillac V8 and 4-speed automatic. I also have a 87 GT V6 5-speed. The funny thing is the V8 can't keep up with the six-cylinder. The V8 is a dog. The transmission sometimes starts in low gear sometimes it doesn't will not kickdown at any speed.


That automatic transmission is completely ruining your driving experience. With a manual transmission connected to the same V8 engine, you'd probably have a smile a mile wide.
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La fiera
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Report this Post12-20-2021 10:57 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
275lbs/ft means nothing if that amount of torque was made at a lower RPM which means the HP would be less as the RPMs increase.
That's the mistake that lots of people do, call out torque figures but not at a specific RPM.
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La fiera
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Report this Post12-20-2021 11:04 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
Almighty 4.9 Big Cubes Cadillac
https://youtu.be/acHe4jAOV6E

VS

My little Supernatural 2.8L
https://youtu.be/dayXz0arXZ0
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Raydar
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Report this Post12-20-2021 11:39 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had the Caddy automatic in my 4.9 car. That trans, even when working properly, didn't do anything quickly. I almost sold the car because the automatic was so uninspiring.
I ended up swapping in a 5 speed trans, and adding the Allante intake manifold. The Allante intake helped a bit, but the 5 speed really transformed the car.
With that said... the ratios are far from ideal. It blows through 1st gear by the time you can blink. And it still runs out of steam by 5K. Just like all the 4.9 detractors will tell you.
But it's still an absolute riot to drive.
The one thing that would make it better would be an F40 trans, with the final drive swap that Fieroguru pioneered. But that's going to run into a bunch of work and money.

But as others have said, it sounds like something is wrong with yours.
For what it's worth, if the throttle position sensor is wired incorrectly, or otherwise defective, the trans will shift at funny times, or not at all.
If the computer is in "limp home" mode, the trans will start out in 2nd gear, and the timing will be at a fixed value. In short, it will be a slug.

Additionally... the 4.9 Caddy has like seven different options (code masks) for burning chips. If someone used the wrong base tune when they programmed yours, it may not be compatible.
I had that same issue with mine, using a chip that someone else had programmed for me. (IOW, it went into the "limp home" mode that I described, previously.)

[This message has been edited by Raydar (edited 12-20-2021).]

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Report this Post12-21-2021 11:40 AM Click Here to See the Profile for BillSClick Here to Email BillSSend a Private Message to BillSEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by La fiera:

Almighty 4.9 Big Cubes Cadillac
https://youtu.be/acHe4jAOV6E

VS

My little Supernatural 2.8L
https://youtu.be/dayXz0arXZ0


Nice comparison.

Think about a four cylinder. My LNF, very mildly tuned - at wheels = 325 whp 347 Tq 2 liter modern engine, lots of room around it. Biggest issue is finding a place to put the intercooler.
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treborerellim
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Report this Post12-21-2021 08:20 PM Click Here to See the Profile for treborerellimClick Here to Email treborerellimSend a Private Message to treborerellimEdit/Delete MessageReply w/QuoteDirect Link to This Post
The reason I went with the Cadillac V8 first place is I ran into a guy that had a 4.9 hooked up to a 4T60 transmission that decided he wanted to go with a Chevy V8 instead and I picked it up for $250. The guy that did the wiring job suggested I order have a 46 t e would be a better way2go and I happened to pick one out of a Cadillac Eldorado engine and trans for 150 dollars. But I can't seem to get all the bugs out of it. As to what suggestion Dennis made in the second paragraph I think you wrote it in Greek, because I don't have a clue on how to do any of it. I guess I'll have to find somebody that really knows what he's doing that can diagnose the problems and correct them. That'll probably cost me a ton of money.

I received a lot of good information and really appreciate all the responses. I kind of doubt I'm going to put my other Cadillac engine in my 87 GT and will probably keep it a V6 as I have 2 V6s laying around and another five speed trans.
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La fiera
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Report this Post12-21-2021 10:30 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by BillS:


Nice comparison.

Think about a four cylinder. My LNF, very mildly tuned - at wheels = 325 whp 347 Tq 2 liter modern engine, lots of room around it. Biggest issue is finding a place to put the intercooler.


Exactly, but that's turbo. It's a different breed. I could make over 400WHP with the 2.8L if I turbo it. Turbos are for individuals who don't know how to make power Naturally Aspirated.

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Report this Post12-23-2021 07:05 PM Click Here to See the Profile for BillSClick Here to Email BillSSend a Private Message to BillSEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by La fiera:


Exactly, but that's turbo. It's a different breed. I could make over 400WHP with the 2.8L if I turbo it. Turbos are for individuals who don't know how to make power Naturally Aspirated.


No, turbos are for when you run out of improvements on a naturally aspirated engine and still want more. Big power in smaller package with better fuel mileage.
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La fiera
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Report this Post12-23-2021 07:17 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by BillS:


No, turbos are for when you run out of improvements on a naturally aspirated engine and still want more. Big power in smaller package with better fuel mileage.


I see your point and makes lots of sense. In my case I'm always trying to come up with improvements for that same reason, not using a turbo.
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La fiera
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Report this Post12-23-2021 11:01 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by La fiera:


I see your point and makes lots of sense. In my case I'm always trying to come up with improvements for that same reason, not using a turbo.
A turbo kind of stops you from thinking out of the box because now you have no limits. But if you limit yourself to non turbo then the your creativity grows. You see how a turbo hinders creativity?


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La fiera
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Report this Post12-23-2021 11:05 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post

La fiera

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Member since Jun 2008
 
quote
Originally posted by BillS:


No, turbos are for when you run out of improvements on a naturally aspirated engine and still want more. Big power in smaller package with better fuel mileage.


I see your point and makes lots of sense. In my case I'm always trying to come up with improvements for that same reason, not using a turbo.
A turbo kind of stops you from thinking out of the box because now you have no limits. But if you limit yourself to non turbo then the your creativity grows. You see how a turbo hinders creativity?
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Dennis LaGrua
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Report this Post12-24-2021 06:13 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by La fiera:

275lbs/ft means nothing if that amount of torque was made at a lower RPM which means the HP would be less as the RPMs increase.
That's the mistake that lots of people do, call out torque figures but not at a specific RPM.

Electric vehicles have little horsepower but full torque starting at 1 RPM and holding thru the RPM range. They are quite good performers with usually fast acceleration. Torque always matters.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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Report this Post12-24-2021 09:28 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The more bottom end torque available directly results in acceleration off of the line.

Torque = Acceleration

Horsepower = Top end
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La fiera
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Report this Post12-24-2021 11:03 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by olejoedad:

The more bottom end torque available directly results in acceleration off of the line.

Torque = Acceleration

Horsepower = Top end


Exactly!!
If Torque = Work and HP = How fast that work is being delivered, the higher in the RPM range you can locate that Torque the more acceleration you are going to have. Because you are increasing the rate/speed of the applied torque/work.
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treborerellim
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Report this Post12-25-2021 08:46 AM Click Here to See the Profile for treborerellimClick Here to Email treborerellimSend a Private Message to treborerellimEdit/Delete MessageReply w/QuoteDirect Link to This Post
I Googled both hijack and tangent and I think my thread qualifies for both. Just saying
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Report this Post12-27-2021 12:03 PM Click Here to See the Profile for BillSClick Here to Email BillSSend a Private Message to BillSEdit/Delete MessageReply w/QuoteDirect Link to This Post
Getting back on topic, the nice thing about a turbo 4 cylinder is that it acts like an NA engine when driven mildly, so you can get excellent fuel mileage but when you punch it you suddenly double the output.

I ran a turbo 88 Fiero for almost 20 years and it was a great combination (mine was a a stroked 3.2 V60.)

Using a modern high tech turbo engine means easier packaging in the Fiero and great power with decent mileage. The naturally aspirated 2.4 available in the Solstice didn't give as good mileage as the turbo 2.0 (unless you had your foot in it all the time.

A lot of people prefer V8s due to tradition, noise, whatever, but there is a lot to be said for the smaller options.
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La fiera
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Report this Post12-27-2021 06:21 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by BillS:
. The naturally aspirated 2.4 available in the Solstice didn't give as good mileage as the turbo 2.0 (unless you had your foot in it all the time.


Bill, is that 2.0 Turbo off the Firefly Pontiac? I'm a fan of the Firefly!
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Report this Post12-27-2021 09:37 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by BillS:

Getting back on topic, the nice thing about a turbo 4 cylinder is that it acts like an NA engine when driven mildly, so you can get excellent fuel mileage but when you punch it you suddenly double the output.

A lot of people prefer V8s due to tradition, noise, whatever, but there is a lot to be said for the smaller options.


Turbos aren't just for 4cyls... they can be put on V8s too!
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La fiera
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Report this Post12-29-2021 10:03 PM Click Here to See the Profile for La fieraSend a Private Message to La fieraEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


Turbos aren't just for 4cyls... they can be put on V8s too!


Yes Guru! Back in the 80's Alfa Romeo F1 engienes where V8 twin turbos. They killed the Ferrari V6, Porsche V6 and Renaults. They would always get fastest laps and pole positions. Their problem was reliability.

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Report this Post01-01-2022 03:20 PM Click Here to See the Profile for BillSClick Here to Email BillSSend a Private Message to BillSEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by La fiera:


Bill, is that 2.0 Turbo off the Firefly Pontiac? I'm a fan of the Firefly!


No, the 2.4 NA engine is an Ecotec. Fireflies were 3 cylinder 1.0 engines or a 4 cylinder 1.3 engines IIRC.
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Report this Post01-03-2022 06:42 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
For advice on the Cadillac, sounds like something is wrong, however, multipled dynos on automatics have shown it to make ~160rwhp.

My 5-speed was making 175 rwhp with the Allante intake. Going to E85 made is jump to 196rwhp and 298 ft*lbs...
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Report this Post01-03-2022 07:13 PM Click Here to See the Profile for RotrexFieroClick Here to visit RotrexFiero's HomePageSend a Private Message to RotrexFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
When I was drag racing I was told torque was for the first half of the track, and horsepower for the second.

For every day driving torque is wonderful, especially in the city, stopping and starting, and climbing hills.

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Report this Post01-03-2022 07:36 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by BillS:

A lot of people prefer V8s due to tradition, noise, whatever...


Never underestimate the importance of "noise" when it comes to engines. If you love the sound of your engine, you get to revel in its glory from the moment it's started, right up until it's turned off.

[This message has been edited by Patrick (edited 01-04-2022).]

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Report this Post01-04-2022 08:58 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by RotrexFiero:
For every day driving torque is wonderful, especially in the city, stopping and starting, and climbing hills.


I now own three diesel vehicles, and the powerbands are just great for every day driving.

 
quote
Originally posted by Patrick:

Never underestimate the importance of "noise" when it comes to engines. If you love the sound of your engine, you get to revel in it's glory from the moment it's started, right up until it's turned off.



My '05 Benz E320 has an OM648 3.2 inline 6. It's not loud, but it sounds good. My '07 Grand Cherokee has a Ben OM642 3.0 liter 75 degree v6. It's not loud either, but it sounds more like a piece of construction equipment... it does not make pretty noises.
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Report this Post01-04-2022 04:00 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:

Ben OM642 3.0 liter 75 degree v6... sounds more like a piece of construction equipment


Thanks, I'll be crossing that engine off my list.
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Report this Post01-04-2022 07:36 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by olejoedad:

The more bottom end torque available directly results in acceleration off of the line.

Torque = Acceleration

Horsepower = Top end


I do feel that when we talk about bottom end torque, we should not be speaking about torque at a specific RPM, but we should be speaking about horsepower at some percentage of redline.

Car engine tachometers could be calibrated in %redline, like this Boeing 737-300 tach:


Is an 8000 RPM redline engine more fun than a 5000 RPM redline engine? If gearing compensates for different RPMs, the driver might not be able to tell the difference between both engines, if the instrument cluster doesn't have an RPM readout.

In my mind, it makes a lot of sense to normalize the horizontal axis of dyno graphs to %redline, for better comparison between engines.
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Report this Post01-05-2022 12:50 AM Click Here to See the Profile for Daryl MClick Here to Email Daryl MSend a Private Message to Daryl MEdit/Delete MessageReply w/QuoteDirect Link to This Post
Would this post be a good place to discuss the pros and cons of long stroke smaller bore engines vs short stroke larger bore engines? Bigger bore allows for larger valves and better breathing. Longer stroke allows for a longer time to more completely burn the air/fuel mixture making for better efficiency.

[This message has been edited by Daryl M (edited 01-05-2022).]

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Report this Post01-06-2022 09:53 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

Thanks, I'll be crossing that engine off my list.


I wouldn't recommend it for a Fiero regardless. First: Diesel. Second: Even though it has an aluminum block, it still weighs >450#. It's built to haul 6000 kg (13,000 lbs) Sprinter vans and other similarly heavy vehicles and vans around Europe... it's built to be beat on constantly. Third: it makes 370-390 ftlbs stock with 450 torks as close as a tune.

 
quote
Originally posted by Daryl M:

Would this post be a good place to discuss the pros and cons of long stroke smaller bore engines vs short stroke larger bore engines? Bigger bore allows for larger valves and better breathing. Longer stroke allows for a longer time to more completely burn the air/fuel mixture making for better efficiency.



Maybe you're thinking "long rod" vs "long stroke"?
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Report this Post01-06-2022 01:35 PM Click Here to See the Profile for Daryl MClick Here to Email Daryl MSend a Private Message to Daryl MEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:


Maybe you're thinking "long rod" vs "long stroke"?


No, thinking long stroke.
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Skybax
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Report this Post01-07-2022 11:14 AM Click Here to See the Profile for SkybaxSend a Private Message to SkybaxEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Dennis LaGrua:

The 2.8L has been road tested to be a 16 second car in the 1/4 mile



I realize its off topic, but throwing numbers around I just want to elaborate, the stock Getrag 5-speed V6 Fiero's are in the 16-second range, while the stock 85-86 Muncie 4-speed V6 Fieros are in the mid 15-second range. I realize that is splitting hairs, nobody cares, and not the purpose of the conversation, but the V6 Muncie 4-speed is just as quick as the stock 5.0 Mustang's from the same era which is impressive, considering they both weighed 2750 pounds and the 5.0 V8 had more power. (Fiero made up difference in aerodynamics and mid-engine layout, verses Mustang loss through driveshaft, solid rear axle, poor traction, etc).

 
quote
Originally posted by Patrick:

If you love the sound of your engine, you get to revel in its glory from the moment it's started, right up until it's turned off.



Yep, while I like the sound of many engine swaps in Fiero's, I still think the stock Fiero V6 sounds really good, especially for the era. My current stock GT sounds better and louder than my previously owned low-mileage GTs, because while it has the original exhaust system like the others, the higher mileage original muffler is probably all carboned up and not doing much sound muffling, combined with a universal high-flow cat, so it definitely gets the attention and quite a few people ask/comment about the exhaust and they can't believe its stock.

[This message has been edited by Skybax (edited 01-07-2022).]

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Skybax
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Report this Post01-07-2022 11:39 AM Click Here to See the Profile for SkybaxSend a Private Message to SkybaxEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by pmbrunelle:
like this Boeing 737-300 tach:


Wooooooooooooooooo, nice.

[This message has been edited by Skybax (edited 01-07-2022).]

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Patrick
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Report this Post01-07-2022 02:22 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
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Originally posted by Skybax:

I still think the stock Fiero V6 sounds really good...


I agree. I quite like the sound of my '86 GT and '88 Formula. My '84 duke, not so much.

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Will
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Report this Post01-09-2022 05:53 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Daryl M:

No, thinking long stroke.


A long stroke engine at 3000 RPM has the same time for combustion & power stroke as a short stroke engine at 3000 RPM.

A long *rod* engine has the piston moving slower around TDC, so it actually does allow (a little) extra time for combustion at high pressure before the piston starts down the bore. This usually manifests as less ignition advance required for best BMEP.

[This message has been edited by Will (edited 01-09-2022).]

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Daryl M
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Report this Post01-11-2022 03:14 PM Click Here to See the Profile for Daryl MClick Here to Email Daryl MSend a Private Message to Daryl MEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Will:


A long stroke engine at 3000 RPM has the same time for combustion & power stroke as a short stroke engine at 3000 RPM.

A long *rod* engine has the piston moving slower around TDC, so it actually does allow (a little) extra time for combustion at high pressure before the piston starts down the bore. This usually manifests as less ignition advance required for best BMEP.



You are correct about the time at a given rpm, but a long stroke smaller bore engine of the same displacement as a larger bore short stroke engine does not rev as high therefore there is more time for combustion.

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pmbrunelle
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Report this Post01-11-2022 06:46 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
The faster an engine revs, the more the contents of the cylinder swish around, so combustion is completed in less time.

So as engine RPM increases, combustion speed also increases; the two effects seem to balance each other, and often spark advance is constant above a certain RPM.
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