FS-DE Extended Specs
- Thread starter igdrasil
- Start date
Speaking for myself, from not only this post, but others, with the experiences and details that you have provided, I'm willing to bet that you (with twighlightprotege coming as a close second) have more exprerience into the tolerences of an engine, specifically, the FS than 99.999% of the people on this forum. No one has provided more intracacies on this motor, especially when it comes to NA applications. I, for one, am willing to place your information higher than that of others.Installshield 2 said:
Excellent post igdrasil!!
Installshield 2
Gothenburg Superiority
Thanks Kevin, seriously...I try to look at it like its "our"engine...and it may be that its a dinosaur that no one ever wanted...But its ours, and we are more or less stuck with it...So rather than complain and rant about how much the FS, or its derivatives, suck, I try to point out that there is potential for certain applications with any engine, including this one...
So I encourage every single person with the means to do so, to not listen to everything you hear regarding this engine (Igdrasil, this is in no way related to the post you just made)...Combustion engines are often lumped into a pile that "general" tuning procedures or modifcations are applied to...but every engine behaves differently, and responds differently to different modifications...a lot of extremely knowledgeable people pop up and give a list of what to do to make X amount of hp from an FS, based on mods they made to their different engine...which is misleading, time consuming, and frustrating sometimes...
But you can always compensate with whatever problem the engine is having...it sucks that it is expensive, but if this is the car that you plan on driving for years to come...its worth it...I guarantee that this engine will hold 8 grand reliably with the right well thought out mods...not saying its cheap, but its possible...that is what is important...
So anyway...back on topic...if you read through that link I posted, you will have noticed that about 15 automotive and mechanical engineers (some of which have extensive experience with F1 and other high rpm engines) stated that piston speed is pretty much a moot point...production procedures have ridded the problems from the past...the 3500 ft/min notion was established in the 60's, and has long since been surpassed on modern OHC engines...
Just wanted to point all of that out to prevent anyone from getting nervous about there engine flying apart because of piston speeds...its not going to happen...and with the right mods it can hold over 1 grand more without a problem...
So I encourage every single person with the means to do so, to not listen to everything you hear regarding this engine (Igdrasil, this is in no way related to the post you just made)...Combustion engines are often lumped into a pile that "general" tuning procedures or modifcations are applied to...but every engine behaves differently, and responds differently to different modifications...a lot of extremely knowledgeable people pop up and give a list of what to do to make X amount of hp from an FS, based on mods they made to their different engine...which is misleading, time consuming, and frustrating sometimes...
But you can always compensate with whatever problem the engine is having...it sucks that it is expensive, but if this is the car that you plan on driving for years to come...its worth it...I guarantee that this engine will hold 8 grand reliably with the right well thought out mods...not saying its cheap, but its possible...that is what is important...
So anyway...back on topic...if you read through that link I posted, you will have noticed that about 15 automotive and mechanical engineers (some of which have extensive experience with F1 and other high rpm engines) stated that piston speed is pretty much a moot point...production procedures have ridded the problems from the past...the 3500 ft/min notion was established in the 60's, and has long since been surpassed on modern OHC engines...
Just wanted to point all of that out to prevent anyone from getting nervous about there engine flying apart because of piston speeds...its not going to happen...and with the right mods it can hold over 1 grand more without a problem...
Keeping stock specs, there is no use for revs higher than 6500. You can see that in most dynos, power starts to get linear at 6400 and drop around 6500rpms and over.
About the MEAN PISTON SPEED damage: this is only a "longetivity issue". If we are going to talk about a 200k mile checkup, our engines will have massive wear in contrast to one with shorter stroke. Piston travels faster generally at any rpm point. 7200 is not meant to be good in our engines, and thats why our REDLINE starts @ 6500rpms, beyond that point, its really stressing. I talked once to the SCCA proteges mechanics and he just told me the same. They rev up to 8k rpms, but the engines does not last the season. They use 3-4 engines for the whole season, because the wear and tear is big. Even using forged internals. The rest of the cars finish the season with 1 engine.
IF you want to go over 6500rpm reliable,you need to make the engine breathe better by either:
1. doing custom valve job to prevent valve float
2. port polishing
3. shorter runners
4. bigger throttle
5. and of course, better piston/con rod assembly.
Ok now, what breaks a motor, is mostly the high revs, but it isnt the Mean Piston Speed...is the MEAN PISTON ACCELERATION. It the tensile (inertial) LOAD that wants to make things go apart and its the tensile strenght what measures internal resistance to break. This load is porportional to the rpm speed SQUARED. TDC is the worst load in the engine. The book Maximum Boost by Corky Bell explains this better.
Thats why IF you want to go HIGH BOOST you will need to RETARD TIMING (or use HIGH OCTANE GAS) in order to move the Peak Pressure a bit later on the power stroke, which is the highest ever experienced on the power stroke and turbo makes the usable power AFTER that. Thats why you can double the power on any engine (with good engine management) and not double the load.
So...in our engines...you want more power, reliable? turbo...and dont rev too high...
if you do things right, a turboed FSDE will last longer than a high reved one.
About the MEAN PISTON SPEED damage: this is only a "longetivity issue". If we are going to talk about a 200k mile checkup, our engines will have massive wear in contrast to one with shorter stroke. Piston travels faster generally at any rpm point. 7200 is not meant to be good in our engines, and thats why our REDLINE starts @ 6500rpms, beyond that point, its really stressing. I talked once to the SCCA proteges mechanics and he just told me the same. They rev up to 8k rpms, but the engines does not last the season. They use 3-4 engines for the whole season, because the wear and tear is big. Even using forged internals. The rest of the cars finish the season with 1 engine.
IF you want to go over 6500rpm reliable,you need to make the engine breathe better by either:
1. doing custom valve job to prevent valve float
2. port polishing
3. shorter runners
4. bigger throttle
5. and of course, better piston/con rod assembly.
Ok now, what breaks a motor, is mostly the high revs, but it isnt the Mean Piston Speed...is the MEAN PISTON ACCELERATION. It the tensile (inertial) LOAD that wants to make things go apart and its the tensile strenght what measures internal resistance to break. This load is porportional to the rpm speed SQUARED. TDC is the worst load in the engine. The book Maximum Boost by Corky Bell explains this better.
Thats why IF you want to go HIGH BOOST you will need to RETARD TIMING (or use HIGH OCTANE GAS) in order to move the Peak Pressure a bit later on the power stroke, which is the highest ever experienced on the power stroke and turbo makes the usable power AFTER that. Thats why you can double the power on any engine (with good engine management) and not double the load.
So...in our engines...you want more power, reliable? turbo...and dont rev too high...
if you do things right, a turboed FSDE will last longer than a high reved one.
twilightprotege
Member
- :
- 2001 323 Astina SP20 (P5)
thanks kevin
Installshield 2
Gothenburg Superiority
According to SCC, those FS race engines see between 8700 and 9200 rpm all the time...and it is true that they need rebuilt a lot...but not every other team does the same...The RTR Spec V spinoff has 100mm of stroke (!!!!!!!!!!) and used to start to fly apart in just 100 miles...but I heard they fixed that...igdrasil said:
Now the fact that our redline starts lower has everything to do with the fact that the stock FS-DE is tuned for torque...the ZE redlines at 7000rpm, and it has the exact same internals (albeit higher static CR)...
I am not going to get into a debate on whether FI or NA is better or more reliable...both can be reliable, and both can be the opposite...but 200k with no engine rebuild is a lot...I know it can be done...but guys planning on making more hp are going to see massive wear by 200k anyway...not just from piston speed and acceleration...
Overall my main point is that if you are extremely concerned about reliability...do not modify your car...
Im glad we are having this discussion. Dont get us wrong. This engine has a lot of potential. See...I posted some videos in the video area...In oct 7 there was an event in one of the reacetracks here in PR, and guess what...the FS-DE powered 323 was the fastest of all, By A LOT!!!!. 10.3s pass in the video, but the best was 9.9s @ 145MPH!!!!!! And the motor is still on one piece.
Im not concerned about reliability. Its just what I have found myslelf and read around about this engine,talking to tunners. Im just telling to STOCK people:
Use this info as you like...it will always help but...Do not rev past 6500rpms except 1st gear, you are wasting your time, there is less power in that area plus hurting the engine. Try it...you will see acceleration is crap after 6500rpms. (except turbo). In the case of turbo, running above 6500 may bend the rods if too much advanced timing is used.
About the ZE redline. Ill need to take a look on the cam profiles.
Im not concerned about reliability. Its just what I have found myslelf and read around about this engine,talking to tunners. Im just telling to STOCK people:
Use this info as you like...it will always help but...Do not rev past 6500rpms except 1st gear, you are wasting your time, there is less power in that area plus hurting the engine. Try it...you will see acceleration is crap after 6500rpms. (except turbo). In the case of turbo, running above 6500 may bend the rods if too much advanced timing is used.
About the ZE redline. Ill need to take a look on the cam profiles.
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since the cost is the same...I would do longer rods! That eventually will need a lower piston pin height which is another PRO.TurfBurn said:
why?, as far as I know...
1. Long rod reduces maximum angle @ 90deg.
2. Help reduce piston side-side movement. less friction
3. Lower piston speed (i think this needs a bit of retard on the ignition because, if its moving slower, peak cylinder pressure comes faster)
So, adding to that, a piston with a shorter pin height will help:
1. Less rocking of the piston (side by side movement), this is basic, and this is good, less prone to damage the walls.
Im not sure about wall clearance in this particular setup, I think it will be the same as any other forged piston (within same brand requirements).
I dont know much so I need more info and experience, what Ive read from MAMotorsports reviews, this is a shorter review, easy to swallow.
I read through what Beau posted too and was hoping to get additional ideas. I'm currently leaning toward the longer rods and pulling my compression back by a few tenths so that I can have some added clearance up top. I'm ordering my rod and piston set tomorrow.
Thanks!
Steve
Thanks!
Steve
I got a question. I just read a little about compression testing, and hear that around 175 is normal for our engine. If atm is 14.7, and compression ratio is 9.1:1, then shouldn't the max compression be 14.7x9.1 = 133.77 absolute pressure, or 119.07 psi above atmospheric. Why doesn't this make sense?
Compression ratio is a more complex equation...I dont have it handy but its very difficult to have a compression ratio given the actual compression of the air on the chamber.
Even Compression ratio changes with leads on fuel.
As far as I remember, some things to have in the equations are:
1. fuel type
2. gasket
3. deck height
4. ring height
5. dome/dish on the piston
6. head
7. stroke
8. cylinder diameter
Even Compression ratio changes with leads on fuel.
As far as I remember, some things to have in the equations are:
1. fuel type
2. gasket
3. deck height
4. ring height
5. dome/dish on the piston
6. head
7. stroke
8. cylinder diameter
Installshield 2
Gothenburg Superiority
one way to think of it is that the timing belt area is actually the front of the engine...and the cylinders start from there and go backwards...the whole transversely mounted stuff gets confusing...
