tom94RX-7

iTrader: (5)

I did a couple pulls on the dynojet today with my water injector spraying into the IC pipe right after the fmic outlet, then switched the water injector to my pre turbo water injection location to get some dyno test results to compare. No other changes were made, back to back dyno pulls. Water only, 24 psi boost, T04R journal bearing single turbo. Attached is a zip file that contains both dynojet files, both PowerFC/datalogit datalog files and my maps/dat file.

Lots of data to compare and interesting results..

Pre turbo WI made an extra 17 max HP. 515 HP compared to 498 HP.
At 6460 rpm it is actually made 48 more HP with pre turbo WI. From 5800-7200 rpm it made on average about 20-30 more HP. Take a look at the dyno files to compare.

Max torque was 431 compared to 416. Again it made about 20-38 more ft lbs of torque through much of the torque curve.

Pre turbo WI slows down the spool up of the turbo a little. Full Boost is achieved quicker with Post IC WI. With Post IC WI it hit full boost at 4520 RPM, with Pre Turbo WI it hit full boost at 4795 RPM.

You can see on the dyno graphs that more power is made with Post IC WI from 4300 rpm up to 5300 rpm. Post IC WI has 34 more ft/lbs torque at 4700 rpm. Power is the exact same below 4300 rpm. The pre turbo WI power and torque curves look much better for drag racing. Post IC WI looks better for street driving.

My AEM progressive WI starts spraying at about 6psi boost at about 3600 rpm and is supposed to have full pressure at about 15 psi (those are my low and high settings). So it is interesting that the Pre Turbo WI doesn't start making more power until 5500 rpm.

The boost curves are a little different looking, the post IC WI boost curve is smoother and logs a tad bit higher boost readings.

AFR's are similar, just a little different but not really enough to impact power alot, AFR's were the same at peak power for both runs, about 11.7 AFR.

Here is a Big difference between the two, Air intake temps.. The AIT's with post IC WI rose from -1C to 9C when I let off the gas. The AIT's with pre turbo WI rose from -1C up to 16C when I let off the gas and then continued to rise to 24C. My FRAITS is also located in my IC pipe after the fmic outlet, prior to the water injector. FMIC outlet, then fraits and then the water injector location. My guess is that the fraits gets wet from the pre turbo WI and that water/moisture has more heat in it which makes the fraits read higher temps?

Knock readings are a little different, not alot but worth looking at.

All thoughts and opinions about all this is welcome.

Turblown

iTrader: (12)

I wish I could remember the results I did 4 years ago, same exact style test. I should go sift through my dyno charts. I remember it being a considerable difference, and it reflected the differences you are seeing. At first I thought something was wrong since the torque curves were very different. Remember one needs to repeat tests to have accurate results. It is best to do back to back, and back to back again.

On a side note just think if you could keep your torque curve more flat on the top end, you would make an easy 600rwhp. I wonder if you need more turbine wheel...

JZG

Excellent info! I always wondered if there was a difference between the two. Since I have pre turbo WI I could never test post turbo of course. It seems to me that the water must be extending the compressor efficiency range to a degree??

This goes part way to explaining how my 60mm compressor made just over 500rwhp on a basically stock engine, as to start with I did not think it possible.

I think the pre turbo power curve on your dyno plot would be better on the road than post turbo, because the hp curve is more linear making for smoother power delivery which is easier to control.

gxl90rx7

iTrader: (1)

good work, this is great info. I like the post IC injection plot better. pre-turbo injection, while shifting the compressor plot to the right, also adds a lot of lag. in the midrange, it lost 30 hp, and about 40 ft-lbs torque. i suppose it just depends on what you want, more midrange or top end

tom94RX-7

iTrader: (5)

Both Post IC pulls yesterday had the same power and torque curve, then just did the one pre turbo WI dyno pull, it was getting late. I do believe more pulls would have shown the same results.

I have switched locations many times but never on the dyno, on the street it did always feel like a little more lag with pre turbo.

I wonder if my turbo is not working very efficient without the pre turbo wi, because the power curve has more dips and not as linear, it definitely looks like it works more efficient with pre turbo wi.

For street driving, the post IC WI will likely just make the tires break loose quicker and easier in 1st-3rd gears.

Howard Coleman

iTrader: (6)

amazing new data! it is nice that we now have some actual results that backs up alot of theorizing. i actually like your preturbo curve as it comes on just where you need it after upshifting.

it still bothers me that you are hitting a piece of aluminum w something very heavy (water), however the dyno is smiling

nice work Tom,

howard

neit_jnf

iTrader: (17)

interesting! I wonder how a dual pre and post turbo setup would do...


a sequential system could be developed with pre and post turbo injecting at different times

tom94RX-7

iTrader: (5)

Thanks. Ya It is nice to have this data for my car now, I switched back and forth a bunch of times last year trying both.

as long as your water injection system works correctly and sprays a very fine mist then the impeller blades should be ok, but I do know for a fact if it doesn't work correctly it will damage your impeller blades as it did mine, I have pics in another thread, I fixed the problem with my progressive controller so that s houldn't or hopefully doesn't happen again.

I would like to do some testing with both pre turbo and post intercooler wi at the same time with two smaller water injectors. I'm using the large size aem nozzle, best all around results might be if I used the small or medium size nozzle pre turbo to get that better efficiency and reduce the lag from the pre turbo wi, along with a small or medium size nozzle post IC.

tom94RX-7

iTrader: (5)

SInce the ait's are higher with pre turbo, perhaps the fmic is just not as efficient at cooling off the moist air. Maybe it gets wet and doesn't cool off the air as good? I also noticed higher ait's last time at the drag strip with the pre turbo wi

Liborek

60-1 wheel at choke limit flows 65 lbs/min at STP temperature and pressure. Cooling at compressor inlet - more density, more mass flow. Compressor itself doesn´t run at higher adiabatic efficiency, but water absorbs heat of compression and so pressure ratio for desired mass flow is lower, consequently turbine power requirement is lower and backpressure is lower. It all adds up for more efficient combination.

While this could be true, that water would condense in the core and basically hinder its efficiency, I would´t give it to much thought, as only temperature which really matters is the one at the end of intake stroke. Especially with such considerable power and torque gains at same airflow/fuel flow.

Mr rx-7 tt

iTrader: (5)

It would be interesting to see a split system comparison, a small shot pre turbo and the bigger shot post turbo.

just startn

iTrader: (33)

Do you plan on testing a few other injections situations, such as the "Dual" setup, pre and post?

tom94RX-7

iTrader: (5)

Yes I would like to test that next time at the dyno, not sure when that will be though.

tom94RX-7

iTrader: (5)

I'm actually trying to figure out why my car is making slightly less power than it was a couple weeks ago. I made 532 HP a couple weeks ago but we found a boost leak at the uim gasket. I replaced the gasket but then my water injector check valve was messed up and my engine was sucking in a bunch of water under vacuum and a puddle of water formed in the IC, it was running like crap sometimes obviously, I didn't know what the problem was yet, I suctioned out all the water and thought it was okay and put it back on the dyno and it made 501 HP (best of 3 pulls), shortly after that dyno session I found the problem with the check valve. I fixed it and it was running good again, put it on the dyno and again it was only making 498 HP with the same Post IC WI setup.

So I don't know if my engine was somewhat damaged from all that extra water going through it, or if the spark plugs could be bad from it? My compression tester gauge is a little messed up thanks to my brother so Idk how accurate it is but it might have a little lower compression than it used to have last time I checked it.

Also I was dissapointed because I put on a full 4" exhaust and a large 1.32 A/R divided turbine housing and new bosch 2200cc fuel injectors and it made about the same max 528 HP with about the same AFR, although the power curve was much better and spool up time was much better.

tom94RX-7

iTrader: (5)

And the only other difference was it was freezing cold out during the last two dyno sessions, I thought it would make more power not less. Can really cold temps actually make less power? Sounds like a stupid question haha.

tom94RX-7

iTrader: (5)

I just did a compression check and I am getting 80 psi in the front and 90 in the rear. Not good..

So any guess on what might have happened inside my engine from all that extra water going through it? When it had that check valve problem it would bog out and blow lots of white smoke and stall out sometimes. Looks like I'll need some kind of a rebuild soon, that sucks, all from a stupid little oring in a cheap check valve in the aem water injector..

silverfdturbo6port

iTrader: (26)

yea that sucks dude. I can only think of too much water as a hydro lock situation and possibly did some damage. That motor has taken its abuse and i always wondered how much back pressure and heat you had with those twin turbos you cranked up. I would assume that they are the ones who did the damage to the motor and when you upgraded you just helped the process along with more pressure

tom94RX-7

iTrader: (5)

Well the motor held up good through all the abuse until this water injector problem, I haven't done a compression check in a while so I don't know exactly how much compression it lost from this problem but I'm guessing it was still pretty healthy before it. Heck it still makes 500 HP haha.

Water injection was good for it for a while, but a little problem from the WI and it likely did damage

Mr rx-7 tt

iTrader: (5)

Tom,
That 10 psi difference is still within Mazda specs and the compression isn't that low. Did you open the butterflies when you did the test?

tom94RX-7

iTrader: (5)

Yes, and had a battery charger on the battery, it was cranking over pretty fast. Same test I did after the rebuild and break in when it made 115 psi. So it definitely lost compression, which I am assuming explains the slight loss in power. And it has even bounces on each rotor face, holding the needle valve on the tester. done in the leading spark plug holes, both leading plugs removed. tested hot/warm after I drove it.

Narfle

iTrader: (16)

I would be interested to see post-turbo, pre-intercooler injection.

just startn

iTrader: (33)

Maybe take exh. mani off and see what you can see.

Mr rx-7 tt

iTrader: (5)

I posted this in Tom's other thread:

The guys at Alky Inj said the test isn't really valid because :

"When you spray pre-compressor we up the jetting vs post compressor alone. Additionally, I didn't read this anywhere. In the end you'll want to do both to get the best result. Not just one or the other."

So you have to vary spray to get the best results. What your test showed was that spay amount was better pre turbo than post. If you would have had different jets you may have had a different result.

tom94RX-7

iTrader: (5)

I think I have read that spraying before the intercooler reduces the efficiency of the IC, so that is the least recommended location. It also may help to explain why my ait's were higher when the water went through the turbo and IC.

tom94RX-7

iTrader: (5)

Are they saying basically that more water is getting to the engine with post IC WI so that extra water hurts power compared to pre turbo? I know a smaller water nozzle size/less water will make more power but I chose to run the large nozzle so that it is getting enough water and because it is the size they recommend for over 450 HP. Sure better results can be had with more testing, but still the test shows that more power is made with pre turbo with the same size nozzle vs post IC.