thewird

iTrader: (8)

Hey Howard, do you know what EGT's you should aim for on 100% gas fuel? Specifically Sunoco 94. I know you run a little hotter when using pump only. I've been getting 1650-1680*F peak on the rear runner pre-turbo. I just had it plugged into my greddy gauge since I still haven't received the FJO converter box to get the front and rear runners logged.

Towards the end of the dyno session every pull started getting leaner and leaner until it started giving 12.5-13 afr no matter how much fuel I added. The fuel pressure was dropping to 40 PSi. The EGT went almost to 1800*F during that last pull before I let off. There was no knock in the logs so no harm done. This was at 16 PSi already. We think its the fuel filter.

thewird

OneRotor

iTrader: (3)

as always Howard, you provide arguably the best infomation on the board. Nice post.

thewird

iTrader: (8)

Finally got my FJO converter box installed. What does it mean when your EGT's are 100 *F apart at WOT and 100-150 *F cruising and idle? I tried adding +0.10 ms lag to the rear secondary injector too see if it would compensate for possibly different flowing ports but there really wasn't a change in the EGT's.

thewird

arghx

iTrader: (3)

^ what leading and trailing timing are you running? Also, it seems like every engine would have at least some variance in temperatures readings between rotors either due to what's going on inside the motor or due to sensor placement and exhaust manifold design. The question is what the acceptable range should be for a given setup.

I actually just got my FJO box hooked up and I am about to start breaking my new motor in soon (provided that I didn't screw up the motor build).

Howard Coleman

iTrader: (6)

'good to see this thread back from the library shelves.

if you fixture dual egts you will typically find around 100 degrees F diff between the front and rear. i messed w lag settings but eventually settled on living w the difference. and yes, the net diff will vary a bit depending on where you are on the map.

BTW, i was on the dyno yesterday and made 506 SAE on 93 octane and meth on a motor i built w advanced port design. egts were max at 1600 at 8500. 20 psi max boost. knock averaged 20 so there is more hp to go. AFRs 11.4. IGL 13.5 w 11 split.

hc

NissanConvert

iTrader: (1)

I've been looking at this Digital EGT gauge, it's 1" x 2" x 3", high temp LED alarm and a relay (for an audible alarm?) offers on the box retransmission in 0-5v (and a number of others iirc). With their heavy duty thermocouples (fast acting- exposed element) it would be roughly $150/ logged EGT, taking up a space of 2" x 2".

94touringFD

iTrader: (30)

What is needed to log the pineapple racing dual egt set up with the datalogit? I'd love to get that and my PLX iMFG wideband O2 hooked up to the datalogit. I plan on getting tuned by Dave at KDR once my motor is broken in and want everything important to be logged, and use my own set up for the tunning.

Monkman33

iTrader: (28)

I dont think you can really log the pineapple setup, unless you have it go from the sensor, to the dataloggit, and then have some sort of output that sends the exact same signal to the gauge. I think splitting the signal would alter the readings... correct me if I am wrong.

thewird

iTrader: (8)

So 100*F difference under WOT is perfectly normal? So when we are aiming for a target of say 1550*F under boost, do we average the two numbers or go with the highest number and work from that?

I'm getting 1730*F on the rear rotor at 8k RPM with ~11.0 AFR's @ 16 PSi with 16 leading/ 10 split (logged timing). maybe my timing is too conservative for that high of an RPM?

Going through a log I did with a a minute or so of WOT through the gears, brake, and then WOT through the gears again, it recorded 1800*F at one point at high RPM.

thewird

arghx

iTrader: (3)

see what happens when you add split (retard the trailing)--it may reduce temps or it may not change them much, but I doubt it will actually make the exhaust run hotter. I've always found that within the normal range of split that people use, the split itself just seems to affect knock levels and do very little for power on unleaded gas. I never had a digital EGT setup until now, and my motor isn't broken in so I can't do any testing yet.

I just don't see how your timing setup is too conservative for pump gas. Mazda runs about 15 split from the factory even on nonturbo rotaries (Rx-8 for example). Remember that they need to keep exhaust temps down under load to keep the cat from burning up, and they need to raise exhaust temps during cold start to reduce emissions. It seems like you would have to have very very retarded timing to actually heat the exhaust up significantly under load. Most of the time the timing is retarded to heat the exhaust up during cold starts.

thewird

iTrader: (8)

I use 94 octane (Sunoco) so I might be better off then most people that don't have that available. But the reason I think my timing is conservative for that high of an RPM is because the PFC base map which is supposed to be something close to the stock map has much higher timing at 7200+ RPM also around a 10 split, sometimes even less. Granted this is the base map and should never be really used for a car and was designed for stock ports and stock turbo's which run out of breath that high in the RPM. Also to note, my boost tapers a tad at that high of an RPM.

To give an idea of my logged timing is (leading with 10 split)... I actually just realized when I tuned it, I had 1 extra degree of timing across the board on high boost but retarded it when I went down to Deals Gap for a little extra safety with the 93 octane fuel but never advanced it afterwards. This is at 16.3-16.5 PSi and drops off to 15.5-15.8 PSi at 8,000 RPM.

<5200 = 13
5200-6400 = 14
6400-7500 = 15
7500+ = 16

My experience with split has been very different. Going from a 14 split to a 10 split gave me a 10-15 rwhp increase across the the board on a Mustang dyno with back to back runs. But for the sake of EGT testing, I will try it since I didn't have EGT logger back then. Also, I noticed increasing the leading timing (maintaining the split) had no noticeable difference in rwhp (possibly because I was already in the sweet spot but I didn't do further testing cause dyno time costs money hehe).

Here's some graphs of my EGT's....

*Red Line is rear rotor and blue is front rotor

Single Pull



Multiple Pulls through the gears (3,4,5 and then 3,4 and another 4)



thewird

Dudemaaanownsanrx7

iTrader: (23)

What is the rest of the setup? Turbo, trim, manifold, a/r, exhaust size, cat, aux injection? I think the more restrictive the setup the higher the egts will be as the heat can't escape easily. You should hook a boost gauge up to several sections of the exhaust to see what kind of backpressure you're getting. A guy on the ausrotary site found a huge restriction in the last section of the exhaust on his car. He cut it off and put a different muffler on and dropped the back pressure a huge amount. I have a feeling this is why howard has had so much lower egt's. His turbo/exhaust setup is very free flowing.

thewird

iTrader: (8)

It's a medium streetport with ported LIM and UIM with FEED bored throttle body. Turbo is an A-Spec 500R-SP with a short runner manifold. The A/R is a 0.84 with a 67 compressor wheel but that is all I know about the turbo. Exhaust is a full 3" with a blown out 3" magnaflow silencer and a Racing Beat dual-tip catback. EGT Probes are within 1" of the exhaust side flange. My methanol system is still not installed so there is no AI at this moment.

Are you suggesting I put on pressure gauges pre-turbo or post-turbo? Pre-turbo would be kinda difficult considering the size of the short runner manifold and I already have the EGT probes on there. I had considered putting one post turbo during the winter but never got around to doing it.

thewird

hsitko

iTrader: (1)

Hey everyone. I have a question regarding the pertinence of these readings. It seems to me that the probes are in an area that is very likely to heat soak and give higher than actual readings. It kind of seems to me that these sensors are only really good for a ball park area of actual egt readings as apposed to a reading that is accurate enough to tune off of. Especeially if it is in a situation like dyno tuning. The first couple of runs will likely look quite different than the last couple. Once everything has gotten hot from full throttle loaded runs the numbers will get a lot higher. Is this even a necessary tuning instrument for our cars? I could see it being a valid monitoring system but the validity of using it as a tuning instrument seems kind of suspect to me. It seems to me that you should be using the shape of your power curve and the location of peak torque to tune your ignition and merely monitor egts, not tune with them. Let me know what you think about this.

--Hank

thewird

iTrader: (8)

EGT's only tell part of the story, the same way AFR's only tell you part of the story. Power curves would be another bit of the story but I don't think its as helpful as EGT's and AFR's. And Dudemaaanownsanrx7 has a very good point about backpressure which I had completely forgotten about since the winter. It's easy to tune a car to be safe with just AFR's and make decent power with generally accepted timing but if you really want to fine tune your machine I think you need to look at all the tuning devices together and make it work.

thewird

Dudemaaanownsanrx7

iTrader: (23)

If you're in a sauna and I put a blowtorch to your arm do you think it will really matter what temp the room is around you? The combustion temperatures are much higher then any amount that heat soaking could account for. So when you make changes to fuel and timing it will show up in egt's. Yes egt is a valid way to tune, whether it's required for tuning is a debatable topic. If egt's are too high you can melt turbo parts and reduce the life of the engine. If they are too low exhaust velocity is lower and reduces spool and probably overall flow. So using egt's can be helpful. Some people tune only using them, others tune using only afr's and some tune using both.

Also by using dual egt probes you can find problems from one chamber to the next. For instance if you're getting misfire but only on one rotor, or one rotor is running leaner then the other for some reason.

As far as the back pressure I would probably start right at the beginning of the downpipe right after the turbo. If there isn't a lot of back pressure then the system from that point back is fine, if it's high then work your way down the system until you find the bottle neck(s). The .84 housing is smallish and could be a source of restriction that's keeping egt's higher, the only way to check the back pressure here is a fitting somewhere before the turbo. The turbo will always be a source of restriction not sure how much before the turbo is considered high though. It's probably been posted somewhere though.

thewird

iTrader: (8)

Oh yah, I forgot to mention a theory I had about the EGT difference. My turbo hotside is jammed right up against the LIM with a blanket. I think that may effect EGT's too because the air would be less dense going to the front rotor. Does anyone have a take on that?

Here's the best pic I have of what I mean, you can kinda see it...


thewird

Dudemaaanownsanrx7

iTrader: (23)

I've heard the LIM has a flow imbalance that causes the rear rotor to run leaner. This could account for the difference if your isn't flow matched or the fuel on the rear hasn't been adjusted. I subtract a little lag with the pfc for the rear secondary injector to try to make up for this and give it a small amount more fuel. I don't monitor egt's though so i can't comment on any temp differences between rotors or if this helps equalize them.

thewird

iTrader: (8)

My LIM and UIM were both ported by hand and port matched to the engine ports so its not stock but the flow imbalance might still be there since no flow testing was done. I did add +0.10 lag on the rear secondary injector but no noticeable difference was seen in the EGT imbalance. I was afraid to add more so there wouldn't be a big power difference between rotors.

thewird

arghx

iTrader: (3)

I'll be interested to see what the EGT spread is between front and rear rotor on my s5 (T2) LIM, which doesn't have the flow imbalance of the s6.

Uncle Hungry

iTrader: (2)

I would like to know who these tuners are using only egt's so I can avoid them like the plague lol. Exhaust temps are great to use as an additional tuning tool but never as a sole source of information.

Uncle Hungry

iTrader: (2)

If you can get about the same psi for boost and backpressure your doing great. If at say 15 psi your seeing 23 psi backpressure, it's time for a bigger turbine housing.

thewird

iTrader: (8)

I don't think its quite as common on a rotary engine due to how knock sensitive our motors are but I've read about it on piston engines before. Usually its done in conjunction with a dyno so you know your heading in the right direction.

Another tuning metric is looking at spark plugs. It's more of a drag thing where only WOT matters and you can shut the engine off immediately after a run and pull the plugs.

But this thread is about EGT's so I think we should keep it at that

thewird

Uncle Hungry

iTrader: (2)

Of course reading plugs is important. I come from piston land and I can tell you, dyno or no dyno, no good tuner will tune with just an egt without knowing afr's first.

arghx

iTrader: (3)

Ok so I've been working on my base tune. At about 2/3 throttle I'm hitting 1650 degrees rear rotor and about 1500 front rotor. This is with a series 5 LIM (no flow imbalance). Boost is about 13.5 psi, leading advance 15 degrees with 15 split, 8.5:1 rotors.

So how hot is "too hot" on straight 93 pump fuel?