BLUE TII

iTrader: (9)

rx7 SE

Had the opportunity to run against an EFR 7670 FD at DGRR over the weekend in my FD still on the sequential system

His setup:
EFR 7670, 10 psi, cosmo irons all else stock porting, high compression rotors, bolt-ons... Dyno'd 300 rwhp at 10 psi. Hits max boost around 2000 rpm.

My setup
Stock seq. twins. PFC, PFS intercooler, RB exhaust, stock everything. Low boost around 11-12 psi and high boost around 14-15.


First run was a 4th gear pull at 2000 rpms. I selected high boost this run and walked away from him rather quickly.

2nd run was the same 4th gear pull at 2000 rpms but this time in low boost. Was a lot closer, he actually out spooled the first turbo by about a car length then when the second turbo came online it looked like I was starting to reel him back in..we ran out of road.

Random 3rd gear pulls in high boost seemed to favor the twins and on low boost went to the driver.


In summary it definitely is a quick spooling setup but it gives up the ghost up top without really turning up the boost. Would be a nice exchange for the twins if wanting to simplify the setup.
__________________


Good comparison!

WANKfactor

iTrader: (1)

Do you know what T-housing he had? Im wondering if the bigger 1.05 wont run out of legs like the .92 seems to do on all the dyno graphs. The 7670 compressor map looks like it should be ok to redline on moderate boost.

gxl90rx7

iTrader: (1)

i was the other driver.. i have the .92 iwg housing

this was the first time ive had it in the mtns since the turbo upgrade, and what a difference it was. i used to have a 60-1/p-trim setup and would always have to drop it down to 2nd. this turbo lets you just leave it in 3rd and still have power out of the turns

Enigmatic

I ran 16psi and about 265rwkw on 98 pump and it was excellent, definitely quicker than my stock twins. The turbo definitely needs more boost to wake it up, right now I'm around 300kw at 20psi on e85 and it's an absolute animal.

KNONFS

iTrader: (14)

Hey man, do you have any logs of your IAT, after a WOT pull?

BLUE TII

iTrader: (9)

No, I didn't save any data logs unfortunately.

What I found though is if I did a 4th gear pull on the freeway the IATs looked pretty close to the 60-1 compressor, but...

on the track because the EFR 7670 was always in boost IATs got really high compared to the 60-1.

I didn't have access to logs (never made a way to secure laptop when racing), but I have never seen an engine bay so hot as when lapping the kart track at 26psi.

Each time I came off track (3min session) and popped the hood the engine bay smelled like hot FG resin from the CF in my engine bay and all the random oils that had been on my UIM over the years evaporated off. You literally couldn't touch anything in the engine bay.

Lag, it lets your IC cool down...

KNONFS

iTrader: (14)

Thanks for the info! Basically, I am retuning the boost controller, and during the last "tuning" I noticed insanely high IAT, enough to stop tuning. Since you are pushing the 7670, was wondering what IAT you were seeing (my problem got me thinking into your situation with the 7670)

gxl90rx7

iTrader: (1)

im going to the track this weekend, i can make a log during a session. im running a ducted v-mount, but only at 10psi

BLUE TII

iTrader: (9)

Thanks for the info! Basically, I am retuning the boost controller, and during the last "tuning" I noticed insanely high IAT, enough to stop tuning. Since you are pushing the 7670, was wondering what IAT you were seeing (my problem got me thinking into your situation with the 7670)

OK, so from what you wrote above it sounds like you ran into the same issue I had of very high IAT after multiple pulls tuning the boost curve?
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I did not see the high IAT during tuning on the dyno with the fan going- in the time it took to map a few changes and do another pull the IC was cooled down sufficiently again (though the exhaust manifold/turbo exhaust housing were another story).

I did see the very high IAT when we did our usual back to back to back pulls at 26psi to see how the power dropped when racing and the IAT were very high- I personally would not do this without 116 octane.

The power loss in the midrange (4,000-6,500rpm) on back to back to back pulls was also quite severe (-25hp 2nd pull and then stabilizing around -35hp from 1st pull), though interestingly the top end power loss (6,500-8,000rom) was the same as my old 60-1 @ 18psi (-15hp 2nd pull and then stabilizing around -20hp from 1st pull peak).

Sounds really bad, but a stock Z06 Corvette loses about 30hp peak from 1st to 2nd pull and the cooling system starts to go critical if you try a 3rd pull on this same dyno/fan.

On the street at 12psi I also did not see this problem- the IC kept up just fine.

KNONFS

iTrader: (14)

That would be awesome, specially since you will be WOT during various gears (similar to what I was doing)

I am sure that I am losing HP, but that's the last of my concerns now My problem is, nothing has changed during the last couple of years (except for the lower PSI wastegate spring), so what exactly is going on, and why?

A WOT 2nd gear pull, to WOT 3rd pull, to 4th WOT pull (up to 5K rpms or so), netted me a 20XF IAT

IAT do come down to their normal temp if I stop boosting.

Found out that the silicone coupler from the turbo outlet to the intercooler had a two small ruptures (not all the way through), where the clamp "clamps" into it. When I pulled the coupler out, there was a third rupture that went all the way through. I am wondering is this has anything to do with it, since my boost signal is getting picked before the TB, and not at the compressor cover, so 16psi on the engine, is not 16psi + intercooler pressure drop at the compressor housing, hence the higher than normal IAT?

I didn't want to wait, so I found a local overprice mishimoto coupler (which is exactly the same Chinese coupler found on ebay, for 1/3 the price), and will be testing my theory soon!

Ahh the joys of not knowing, and troubleshooting in the dark

BLUE TII

iTrader: (9)

Ah, gotcha.

Yes, boost leak = very high IAT.

Your compressor has to spin faster and move much much more CFM to make the same boost so it shifts you directly horizontally way over to the Right on the compressor map (flow and compressor rpm rise PR stays the same as normal).

gxl90rx7

iTrader: (1)

i took some logs today at the track running 10psi boost.. road atlanta with 90F ambient. intake temps topped off around 130F, but that is with a well ducted vmount and true cold air intake

KNONFS

iTrader: (14)

Fixed the coupler, and MAX IAT went down by 20F, but they are WAAAAY to high. Something is going on, and I am not sure what. Unfortunately, I lost the HD on my laptop about 6 months ago, and lost all of my logs from last summer. Going by memory, I never had such high IATs, although, I was also running 13-14psi, instead of the current 16psi.

Thanks for the info! Do you have a FC? if so, any pics of the true cold air intake? I am just running a filter on the turbo, so there is room for improvement on my side.

gxl90rx7

iTrader: (1)

its an FD, this is an old pic, but you get the idea.. i have since reworked it, the radiator sits a little lower and IC is slightly more forward. I added ducting on the sides, and the power steering line is relocated to behind the radiator

after running a vmount for several years now, i am noticing the fins on the radiator are all bent, either by debris or just air hitting it hard.. probably hurts cooling capacity. the fans do cycle on every 5 minutes on the track

how high tdo your intake temps get? when i used to track my old FC it had an ARC top mount, and temps would get up to 150F but i didnt have any problems, it made somewhere around 330whp. it is interesting my FC with the factory radiator setup, mostly factory ducting, and A/C condenser would overheat on the track after about 15 minutes.. this FD with a vmount runs cool as a cucumber

KNONFS

iTrader: (14)

Ahhh, a FD, NICE! I've been thinking about setting the radiator in the FC in a more upright position (instead of slanted), and running the air filter through the new gap created between the radiator and the OEM radiator frame support.

Prior to fixing the teared coupling, I saw IAT of 203F after WOT from 2nd to 4th (not doing a full 4th gear pull). After fixing the coupling, same pull nets a 180F

BTW - Will check the pic from home, cant see it from current location.

BLUE TII

iTrader: (9)

If you had a boost leak for any length of time, check inside your intercooler for oil puked out by the turbo compressor during the overspeed.

If you have a bunch of oil in there and clean it out the IAT may go down some (others have reported this anyways).

KNONFS

iTrader: (14)

There was some oil, and I went ahead and cleaned the intercooler with acetone, same with the IAT(and its surrounding areas) when I replaced the coupler.

BTW - I didn't mean to highjack your thread

I have a possible lead. On my commute from work, I kept going back to what has changed from last year, and other than that wastegate springs, was there anything else? And then it hit me, the radiator fan used to run at 100% at coolant temps above 180f, and not to long ago, I changed the efan from running 100%, to running on duty cycles based on coolant temp.

I guess its possible that the efan was pulling air through when it was running constantly at 100%, and it was helping with the efficiency of the intercooler... maybe?

Good thing that its very easy for me to test such theory

Again - sorry for the thread highjack

BLUE TII

iTrader: (9)

BTW - I didn't mean to highjack your thread

NP, as stated earlier the thread is a free for all and I don't mind.

The fan sounds likely. Is this intercooler mounted in front of the radiator?

KNONFS

iTrader: (14)

About .5" to .75" from the radiator.

Since my intention was not to cluster your thread, I didn't provide all of the data on my setup. I've ben running a water cooled intercooler, fairly large radiator (scirocco radiator by AFCO), and the smallest Chinese intercooler available (been running this setup for 4 years)

Turblown

iTrader: (12)

Not exactly a back to back, but worth showing in my opinion. I tuned both cars this morning within 15 minutes of each other. Red line is a stock port FD on pump gas, with a high flow cat with our efr 7670 cast kit. Blue is a medium street port fd on e85 with full 3 inch exhaust, our tdx57 on a short runner re amemiya manifold. Open 50mm wastegate. Both cars have same size billet compressor and same size turbo manifold runners. Tdx57 has a overly big 1.15 a/r with a p trim turbine( 74mm vs 70mm efr)

BLUE TII

iTrader: (9)

Finally took down the engine from this car as I have found someone to take on the shell.

Only damage is the cracked front iron...

Wear-
The front iron that I had lapped and WPC treated as an experiment shows the same wear (negligable- can barely feel a step with the pad of your finger) as the new side housings, but did rust in the 2 years sitting around whereas the new side housings (nitrided) did not rust.

I would have no objections to putting it back together with a new front housing and running it, but it is going into storage for an indefinite time.

zaque

I don't understand where you guys talk about needing higher PSI for the same output.
Are you measuring boost where it exits the compressor, so a smaller diameter compressor will have a higher PSI for a given amount of airflow?

... Doesn't that not matter one iota to the engine?

Isn't what matters the CFM? If you have a small compressor, the air is going to expand more by the time it exits your intercooler.

If that's how you're measuring airflow, then shouldn't 20psi from the 7670 be equal to 15psi from the 8374, and the 20psi from the 7670 is probably reliable on pump gas...?

RGHTBrainDesign

Really cool question.

I'm thinking Hydrostatic Principle and Bernoulli's Equation.

P1A1V1 = P2A2V2...

Interested to see what you guys find out.

Tuning4life

iTrader: (2)

Power comes from pressure and temperature of the incoming air, also, larger turbo's typically have larger turbine wheels which means less backpressure.


At certain boost levels given the same displacement engine the air being emitted from the turbo will have different temperatures given the efficiency of the turbo.


hence why certain turbo's make more power at higher boost levels than others, but when run at the so called threshold points both turbo's can make roughly the same power.


so a smaller turbo might be pretty equal to a larger one around 15PSI or less and when you hit that threshold level the larger turbo starts making more power due to efficiency and less backpressure. hence it has more dense (colder) temperatures at that pressure.

BLUE TII

iTrader: (9)

Originally Posted by zaque View Post
I don't understand where you guys talk about needing higher PSI for the same output.
Are you measuring boost where it exits the compressor, so a smaller diameter compressor will have a higher PSI for a given amount of airflow?

One can't think of the turbo/engine relationship as a static formula.

For example engine VE is affected.

The smaller turbos smaller exhaust side will lower the engine VE and thus lower the CFM required for the same boost level on the larger turbo (or raise the resultant boost pressure of the same CFM flow).

Another example is compressor efficiency.

The smaller 7670 compressor is spinning faster to produce 53lbs/hr at 64% efficiency (~20psi) and the larger 8374 compressor is spinning slower to produce 53lbs/hr at 75% efficiency (~20psi).
11% denser air charge on the larger compressor at the same CFM and same boost pressure, so it makes more power.

Then you also have total system heat soak.

The smaller turbo spools quicker and sooner and at lower vehicle mph and in addition has lower efficiency at high CFM output.
Great, but this all leads to much more heat into the intercooler, radiator, oil cooler, engine block, etc over time which lowers peak output in actual use over a laggier turbo that puts less heat into the system.