Well I've gone through my 5th engine and 2nd turbo engine in this car and the rear rotor is completely compressionless. I have a low milage S5 NA engine and good housings etc but this engine may have eaten my last set of turbo rotors.

I'm thinking of using my known good set of S5 NA rotors when I rebuild it again.

In no way is my setup stock, to name a few things there's a knightsport turbo, 3in back exhaust, fmic, Rtek 2.1 engine management, 720 primary injectors, and 720 secondaries, wideband afr, and a dual egt gauge for the front and rear rotor.
Obviously the engine would have more compression due to the higher compression ratio rotors but this engine is also ported pretty good and that will lower the compression back down a little. I'm expecting probably no more than 120 psi of compression.

Now I know people have done succesful complete NA turbo engines with pretty good hp numbers with the correct tuning.

You guys have any idea on the changes I'll have to make in my fuel map to componsate for the higher compression ratio and the new safe boost levels? I do have access to a dino too

 

I run S4 NA rotors (9.4:1) in my streetported T2. Seems safe up to at least 8-10 psi on the stock load based timing map on the rtek 2.1 w/ 4x720cc/min injectors on my stage 4 BNR Hybrid. I am able to boost about 13psi on my MAP based timing map that still needs some work. I think I can still up the boost some but I'm scared cuz my pre-turbo egt is over 1000 C by 6000rpm.

9.7:1 is pretty high though. Do it and tell us how it turns out. I've got 30,000 miles and counting on my high compression turbo. I'm considering going 9.7:1 on my next build if I decided to build it for E85.

 

man you guys saved the day, i was really undecided about my car being able to run, like chris, i blew my all turbo engine and only the rear housing and rotor were bad, so i replaced the housing and the rotors with S5 N/A rotors and S5 housing because i wanted to put the knock sensor on the housing itself, i'm also getting the Rtek 2.1 and i need a favor from you guys, let me know what you think, i'm getting the rtek tomorrow and hopefully have it before thursday, i'm moving this weekend and i need to be able to drive the car but i don't have a wideband to tune the car yet. i probably need to drive the car about 1 mile at most, it's a fresh rebuild, and i don't want to blow it up by running too rich, or too lean, my set up is pretty much stock other than 3" downpipe and testpipe, intake,Apexi BOV, and a mild streetport, do you guys think i'll be able to drive the car if i just plug and play the rtek and not correct anything but cranking map to start up the engine? or do you guys have any suggestions on how i should correct points below 3k rpm? i'm also new with the rtek but i've done as much reading as i could find before i buy it so please i'm open to any suggestions

 

stay out of boost and you'll be fine

 

i know that, but the car won't start with the stock computer because it's receiving way too much fuel, if i crank it it'll flood and if i turn off the fuel pump, it'll clear the flood, start up, i turn on the fuel pump, but it'll die again since it's still getting way too much fuel, then i thought of using an S4 N/A computer, but it still won't work, so once i get the rtek i'm going to have to lean out the mixure a bit, the thing i'm concerned is that i may lean it out too much, so is there anything on the rtek that can somewhat tell me the fuel mixture? i'm running the 550 injectors

 

i'll take two tickets for the 8.5's please.

and @ engine number 5, its too lean, too much timing, or you have some other issue like the NA plug wires crossfiring or something

 

Common problem. Run the rtek ecu with 550 primarys, 680 secondaries out of a GSL-SE. It's a common high compression setup for the stock turbo. That should get the car running to the point that you can start to tune it with the rtek.

If you have spare cash, i'd recommend a pre-turbo EGT gauge and wideband sensor down the downpipe a little bit.

I'd eventually switch to 4x 680's to be on the safe side. High compression drinks gas.

If its not the fuel, like j9fd3s said, double check your timing.

 

ok, everybody keeps telling me what set up i should run, although i do appreciate the suggestions, i can figure out what set up to run on my own, my main question has not been answered, can i tune the car only using the rtek and viewing the logs? just so that i can drive the car to where i'm moving?and if yes, how i do so? and of course i will get a wideband and temp gauges asap, but i don't have the cash right now and need to move the car

 

set it to 720/720 preset and if everything is mechanically sound it should at least start, idle, and drive well enough to move under its own power. There's nothing wrong with that injector setup. The Rtek can handle it fine. Use the idle set procedure in the Rtek to adjust the BAC vale and variable resistor. Go ahead and load up my high compression turbo timing maps into the Rtek as a starting point. You could pull even more timing (due to 9.7:1 AFR and 91 octane) but IMO I don't think that's necessary. This is significantly retarded from the basic timing advance in the factory load-based map.




Now did you read the Rtek 2.1 manual? Did you look in the Rtek section? Do you know how it works?

 

I'm going a similar route with my build too. Plan to rebuild with 9.7 rotors and if budget allows they will have 3mm seals. The main thing you have to do with high compression rotors to keep your setup safe (from what I've gathered so far) always use highest octane available as a safety precaution, fix your timing to compensate for boost (more so than lower compression) and watch your EGT's (I'm going to try to invest in an Aux Injection kit as well just to be on the safe side).

 

yes, i read throughout the entire manual, and i have automotive experience, i just don't have experience with tuning that's why i'm asking a bunch of questions about it. Like how do i know how much timing to retard or or advance, or leave it alone, i know why i would have to richen or lean the mixture, but i'm not too experienced with the why i should adjust timing, if anybody has a link to a thread of tuning please post, and sorry for thread jacking... but i hoe all my questions are useful to chris

 

Subscribed. When I blow my Jspec, I want to use my old NA rotors in my build.

 

if you don't have a way to read a trustworth knock sensor, generally speaking you start with a known "safe" map. then you get on the dyno and start advancing the timing a little bit at a time until the car won't pick up any more power. then you back it off some. or if you are hearing knock and/or seeing it on the sparkplugs you back it off some. Ignition tuning is a big big topic. Look in the single turbo archive section, there are two good threads in there. Basically as rpms increase, timing advances. That is like centrifugal advance on a very old distributor. As boost increases (or manifold vacuum decreases), timing retards. That's equivalent to vacuum advance on an old car with a distributor.

Combustion chamber design, intake air temperatures, compression ratio, and fuel quality all affect timing as well.

 

i looked in the single turbo section but i didn't see anything related to "how to tune timing" will i be ok if i just run the factory set up on the r-tek if i run 8 psi on the 9.7:1 rotors? and on the rtek 2.1 you can view the values on the facotry knock sensor, is this accurate engough to use it as a tuning tool?

 

If I recall, stock timing can be quite dangerous at higher levels of boost because it does not retard the timing in proportion to boost.

Someone else can probably elaborate.

 

that's for N/A computers, i know that turbo II computers will retard timing by 1 degree every 1 pound

 

N/A computers don't compensate for boost changes, turbo II computers will retard timing 1 degree every pound i think, i'm not sure how much it retards it, but i know for a fact it does

 

thats why you use water injection.

 

since you are going to use an rtec 2.1 why not just down load arghx's map. if you read his post he says you may not need to pull more timing out of it. His map would be better and safer to run than the stock t2 map. I'm going to use arghx's map for my microtech lt-10s as a base line, and will most likely pull another 3 degrees out of it like he suggested to me. If you couldn't tell i'm also building a s5 6 port turbo. good luck the original poster and you sir.

 

ya i've also decided to go the same rout mate, but what do you mean you'll pull another 3 degree? you mean you will retarn the crank angle sensor by 3 degrees? or on the rtek at certain boost and rpms? please elaborate

 

As a follow up from last year when I first started up this thread I'll let you know what I did.

The S5 rotors were of course lighter and did have higher compression. I used them in one of my cars I had and have since sold. Once the engine was broken in I was seeing 125 psi for compression. Dunno if thats good or bad, high or low because I've given up on trying to figure out the point in which a rotary engine engine doesn't have enough psi to fire. One of my TII engines have 60 psi of even compression. It always fires right up and pins you in the seat, so no problem there. Anyways,
The high compression engine was all S5 13BT aside from the rotors. I of course bought an Rtek 2.1 setup for it like I do for all my turbo cars and ran 720 injectors all round, wideband O2, stock S5 turbo, built exhaust, etc etc, the usual turbo car stuff under the hood. The dyno showed a respectable HP of 270hp at 6Kish rpms and 10psi. I spent a day tuning it and used the stock load map but retarded the timing a bit at the CAS. It was however a more stock engine than built engine meaning stock porting, TMIC, stock turbo, even stock TID and airbox and all. So 270hp was nice to see out of that engine. I didn't spend money on an EGT because I had a little faith in my tuning and that at 120 psi of compression I would be alright since the FSM said those numbers were very close to stock turbo engine high compressions.

Oh because someone will ask... yes S5 engine, S4 car, S4 fuel injection.

So, results may vary, some assembly required, recommended adult supervision, ages 12 and up, batteries not included.

 

well i am going to change the values directly on the load map when i load it onto the microtech. after i do that i'm going to make sure to keep the split the same as it was before so that means i will have to change the values on the trailing map. Here is the link where i got this info from, look at posts 10-14: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-6-port-turbo-whos-done-questions-inside-890359/

 

why not just change the split and leave the trailing alone? or do you have a particular reason you don't want to touch the split map? and i had seen those posts before but thank you for the link anyways i appreciate it

 

https://www.rx7club.com/single-turbo-faq-122/advancing-timing-high-rpm-101226/

https://www.rx7club.com/single-turbo-faq-122/how-many-run-no-split-timing-325400/

 

RotaryRocket88 has generously provided a portion of the factory s4 T2 timing map:



It's a little different to read than the boost-based timing. Load is most likely proportional to airflow divided by rpm, at least according to the series 3 GSL-SE training manual:



That kind of calculation is common. Most airflow-based systems calculate the load unit in some way that is proportional to airflow divided by rpm. The exact calculation depends on the car or manufacturer. On Subarus for example the basic calculation is pretty simple:

MAF grams/sec (taken from the MAF voltage and the airflow lookup table) * 60 seconds / rpm

That's a bit of an aside, sorry. Anyway if you compare the numbers in that factory map to the leading map I have posted above you can see that my map continues to pull timing as boost increases while the factory map "flattens out" as airflow increases, looking up across the vertical axis. The factory map is also more aggressive at higher rpms. The key to understanding timing maps it to look at the rate of timing change across each axis. It's basically really simple derivatives if you have taken any calculus. A timing map is a 3 dimensional thing and it has multiple derivatives if you want to think about it that way.

With different setups the rate of timing change across each axis will change (1st and 2nd derivative of the curve). It's a slightly different thought process on airflow based maps (Rx-8, Evo, STi, stock FC) than on boost-based maps. So on a boost-based map, if I have a ported engine and a large efficient turbo I am probably going to reduce the rate at which the timing ramps up across the rpm axis. If I have better fuel quality or lower intake temps I may be able to add timing across the board to a large matrix of cells. Compare these two boost-based leading maps:




Look horizontally across at each boost level, and then look vertically across each rpm. See how the progression is different? That's your rate of timing advance or timing retard. It's pretty much the first derivative of the timing curve. And then as engine parameters change, I adjust the second derivative of the curve--how fast of a timing increase is occurring. Now I'm just kind of doing this by eye, but some Subaru guys will go hardcore with the spreadsheets, derivatives, and smoothing functions.