Pettit Super Charger Owners
12-22-2008, 08:21 AM
#4076
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Phil
I think the thread should stay here. The hate-ing turbo wannabe folks don’t bother me at all. In fact, it encourages me to keep looking for better ways to refine my SC RX8, which btw is a fine product just out of the box. Too bad that they clutter this thread with useless information in order to distract and overshadow the good stuff. But then I don’t go to their threads to point out how many renensis turbo engines are destroyed in less than a couple of thousands of miles due to extreme exhaust heat and bad performance. Just look at the parts sales thread and see it for yourself. Notice how many turbo kits are for resale at any given time. Facts, just facts. Bottom line, the Pettit SC a is simple out of the box kit and durable as long as you don’t go making modifications without first addressing AF ratios. The same applies to a turbo setup if you address the exhaust ports first which entitles you to take the engine out of the car. In my case I decided to keep the engine in the car and just bolt in the SC kit. My personal goal was to have a 300 whp RX8 (done), reliable FI RX8 (done), fun to drive RX8 (done). It just happens that I finally have time to work on my R100 since there is practically nothing else to do on my Pettit SC RX8.
I think the thread should stay here. The hate-ing turbo wannabe folks don’t bother me at all. In fact, it encourages me to keep looking for better ways to refine my SC RX8, which btw is a fine product just out of the box. Too bad that they clutter this thread with useless information in order to distract and overshadow the good stuff. But then I don’t go to their threads to point out how many renensis turbo engines are destroyed in less than a couple of thousands of miles due to extreme exhaust heat and bad performance. Just look at the parts sales thread and see it for yourself. Notice how many turbo kits are for resale at any given time. Facts, just facts. Bottom line, the Pettit SC a is simple out of the box kit and durable as long as you don’t go making modifications without first addressing AF ratios. The same applies to a turbo setup if you address the exhaust ports first which entitles you to take the engine out of the car. In my case I decided to keep the engine in the car and just bolt in the SC kit. My personal goal was to have a 300 whp RX8 (done), reliable FI RX8 (done), fun to drive RX8 (done). It just happens that I finally have time to work on my R100 since there is practically nothing else to do on my Pettit SC RX8.
12-22-2008, 11:55 AM
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Hows this, if you havent owned or still own one or have (driven with installed in your car and or ridden in it for more then 1,000 miles or instaled one your self, (yes you Charls).
All that said if any of that dosnt apply to you or you wanting one, or having a improvment, stay out. Im going back and editing a bunch of junk out myself. 09/27/07 is when it was started, dam.
All that said if any of that dosnt apply to you or you wanting one, or having a improvment, stay out. Im going back and editing a bunch of junk out myself. 09/27/07 is when it was started, dam.
12-22-2008, 06:02 PM
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Well, whats so hard about reading the title of the thread. We have people comming in here giving false info on how to fix a problem like the one about a hole in Gregs tunning when it was his cat failing. When you go and missdirect someone it tends to cause problems especialy when they were wrong and miss leading. Id say thats in the direction of setting someone up to fail at his mission that hes trying to accomplish. Unless there in here to try to sell you somthing that you dont need, who cares if it blows your motor, the sale was made type of attitude is screwed up. Incase anyone dosnt see my point about it being a big deal if your cat fails think about your exaust ports and the effect of back preasure and heat. Not an issue that can be tunned out.
12-22-2008, 06:10 PM
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anyone with a cat on a boosted car isnt serious about it anyway..? you arent going to serious power levels with a cat, and you arent going to have a lot of reliability in a cat in a boosted application
12-22-2008, 06:21 PM
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i cant imagine living there.... ughh.... though if i was in that position, i'd mcu rather go to the trouble of swapping for inspection time and hoping i didnt get caught otherwise, than to risk not noticing it failing and start destroying the motor
12-22-2008, 06:34 PM
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Well, the only option that I can think of since every cat ive heard of on an RX8 seems to fail is maybe looking into ones made for diesels, they can withstand higher temps and probly last alot longer. Anyone have a powerstroke aftermarket cat sitting around. Might be a good place to start. My car is down or id jump on the wagon with that.
12-22-2008, 07:55 PM
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whats funny about that? making any kind of serious power you cant keep EGTs down enough for any kind of cat life
yeah it'd be nice for a lot of people to have some sort of FI cat option besides the VERY expensive stuff that TeamRX8 got to work
Well, the only option that I can think of since every cat ive heard of on an RX8 seems to fail is maybe looking into ones made for diesels, they can withstand higher temps and probly last alot longer. Anyone have a powerstroke aftermarket cat sitting around. Might be a good place to start. My car is down or id jump on the wagon with that.
12-22-2008, 08:11 PM
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Who said replacing the cat was a problem...The one I took off, I've already gutted for replacement of the one I just put on. Id rather be replacing an inexpensive cat every couple years than my engine because of the EGTs caused buy a turbo...
12-22-2008, 08:16 PM
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wow, really? hot air in = hot air out. remind me how more efficient your compressor is than than a turbocharger. i'm done, anyone who has any ties to a turbocharger has no credibility here. hypocrits
Last edited by paulmasoner; 12-22-2008 at 08:21 PM.
12-22-2008, 08:35 PM
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The EGTs on our cars are most likely the same, the cat was at the end of its life...
I would just rather not have the backpressure of a TC and have to run the risk of exhaust port failure, ie replacing my cat every couple years is a minimal cost IMO since so far most of them show the same surviability... And considering where I live is the second most resitrictive state behind Cali on emissions I do what I can to keep it a DD...
I would just rather not have the backpressure of a TC and have to run the risk of exhaust port failure, ie replacing my cat every couple years is a minimal cost IMO since so far most of them show the same surviability... And considering where I live is the second most resitrictive state behind Cali on emissions I do what I can to keep it a DD...
12-22-2008, 08:45 PM
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To be EGT or not to be AFR, that is the question.
Well here’s a little light reading for y’all.
Enjoy.
There seems to be a lot of mystery and misinformation about using exhaust gas temperatures to tune engines. Claims by many EGT gauge manufacturers about it being the best way to tune an engine must be qualified. The BEST way to tune an engine is on an engine dyno- PERIOD. What EGT is good for is a reference for where the engine made maximum torque at wide open throttle. Once removed from the dyno, a similar air/fuel ratio can be established at a later date by dialing in the mixture to achieve the target EGT. It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 12.0 and 13.5 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.
It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can't guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.
Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.
You can sometimes feel a lean of peak condition as the mixture is hard to ignite and power will be down a bit as well. Once the AFR gets close to 17 to 1 at WOT, generally the engine will start to lean misfire. Most tuners always recommend to begin jetting or programming from a known very rich initial setting and carefully leaning until torque falls off slightly, then going back richer to the point of max torque. Note the EGT at this setting. Be aware that altitude, barometric pressure and ambient air temperature may affect this optimal temperature to some degree.
Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are supposed to be highly accurate and everyone has jumped on the bandwagon with these lately. Unfortunately the naive and impressionable often don't question the accuracy of these devices. We have seen some dyno plots indicating best power was achieved at AFRs of 9.7 to 1 on gasoline. This is PHYSICALLY AND CHEMICALLY IMPOSSIBLE and shows that either the sensor was bad (leaded fuel used possibly) or the meter was not calibrated properly. Again, the wide band sensors have the same limitations as the narrow band- leaded race gas quickly fouls them. We have heard and read many stories now indicating that certain brands of wideband meters differ as much as 2 points AFR in readings between each other. In other words, the accuracy of some of these devices is highly questionable. Extensive testing with laboratory quality instrumentation on aircraft engines universally indicates that best power is NEVER made at AFRs richer than 12 to 1. Airflow and fuel flow rates are independently measured and each cylinder is instrumented with EGT probes.
Well here’s a little light reading for y’all.
Enjoy.
There seems to be a lot of mystery and misinformation about using exhaust gas temperatures to tune engines. Claims by many EGT gauge manufacturers about it being the best way to tune an engine must be qualified. The BEST way to tune an engine is on an engine dyno- PERIOD. What EGT is good for is a reference for where the engine made maximum torque at wide open throttle. Once removed from the dyno, a similar air/fuel ratio can be established at a later date by dialing in the mixture to achieve the target EGT. It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 12.0 and 13.5 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.
It should be mentioned that the target EGT is valid only on the same engine configuration as was used on the dyno. If you change the ignition timing, cams, pistons, headers etc., the optimum EGT may also change. Raising the compression ratio with no other changes will drop the EGT at the same AFR. Retarding the ignition timing will generally raise the EGT at the same AFR. One engine might make best power at 1350 degrees while a very similar engine might be happier at 1500. You can't guess at this or you are simply wasting your money on the instrumentation. Wankel engines have higher EGTs than comparable piston engines due to their lower thermal efficiencies. 1800F is not uncommon here.
Some gauge manufacturers say you should tune to achieve maximum or peak EGT for maximum performance. This is incorrect. Peak EGT generally occurs at an AFR of around 14.7- 15.0 to 1 on gasoline. This is far too lean for maximum power and is dangerous under continuous WOT conditions. Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.
You can sometimes feel a lean of peak condition as the mixture is hard to ignite and power will be down a bit as well. Once the AFR gets close to 17 to 1 at WOT, generally the engine will start to lean misfire. Most tuners always recommend to begin jetting or programming from a known very rich initial setting and carefully leaning until torque falls off slightly, then going back richer to the point of max torque. Note the EGT at this setting. Be aware that altitude, barometric pressure and ambient air temperature may affect this optimal temperature to some degree.
Are EGT gauges better than AFR meters? Conventional narrow band oxygen sensors and digital LED meters are not the best devices to measure AFR in the richer ranges but they certainly warn of a too lean condition immediately and obviously, without translation by the driver and they are affordable. Meters combined with wide band sensors are supposed to be highly accurate and everyone has jumped on the bandwagon with these lately. Unfortunately the naive and impressionable often don't question the accuracy of these devices. We have seen some dyno plots indicating best power was achieved at AFRs of 9.7 to 1 on gasoline. This is PHYSICALLY AND CHEMICALLY IMPOSSIBLE and shows that either the sensor was bad (leaded fuel used possibly) or the meter was not calibrated properly. Again, the wide band sensors have the same limitations as the narrow band- leaded race gas quickly fouls them. We have heard and read many stories now indicating that certain brands of wideband meters differ as much as 2 points AFR in readings between each other. In other words, the accuracy of some of these devices is highly questionable. Extensive testing with laboratory quality instrumentation on aircraft engines universally indicates that best power is NEVER made at AFRs richer than 12 to 1. Airflow and fuel flow rates are independently measured and each cylinder is instrumented with EGT probes.
12-22-2008, 09:12 PM
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Id like to add to the subject. If you have restriction in your exaust system it keeps the heat between that restriction and your engine. So the better the flow out the less heat stays in. Even if you have 1400 EGTs its better to have it exit then linger.
