Tuning turbo and flat top pistons for 10 psi results

[letitsnow]

You might try a non-projected tip spark plug, stock is something like BPR6ES-11 or something similar, leave out the P.

 

How does the car feel with the timing you've got so far?

[roger280zx]

The angle of the air hitting the front of the intercooler matters none if the majority of it will not pass through because it cannot be drawn through because of the eddys behind it. Your oil and water temps will thank you as well. As to the internet misinformation I agree and we should ALL check before we go posting about some ones set up and trying to help them with their detonation issues. I would hate someone's motor to go boom because I was running off at the keyboard.

[dexter72]

Datsun Deron, Ok cool. Try the gaps at 25 and see how the engine responds. At one time I was having a really hard time with an engine ping and pre-ignition at the same time. I checked the gaps on my plugs and they were all over the place. So i closed the gaps and the pre-ignition went away. Then I could get the pinging out.

 

I think the plug heat range depends on your engine. Some can handle 2 ranges colder and some can't. I'm just doing 1 range colder.

 

On those lower bins in your tune. I used to get popping out of my exhaust while decelerating, when my bins were in the 30's.

[aarang]

I agree with letitsnow, I had to run non-projector tip spark plugs. I have NGK BR8ES's gapped @ .030 in there now.

[Gollum]

FYI, Nissan rated the 75 to 80 L28 as 8.3:1 (N42 block with dished pistons and N42 or N47 head). Then 8.8:1 in 81 to 83 with the F54 block with flat tops and a P79 head. 7.4:1 for the turbo with a F54 block with dished pistons and the P90 head. Yes, the P79 and 90 have the same size chambers.

 

Thank you for the clarification, for some reason I'd never seen the distinction laid out but now that you mention it that makes total sense.

[Datsun Deron]

@ arrang - Thats a great point, I'm running the stock 280zx turbo camshaft I can't confirm the stamp on it. I've got quite a few spare non turbo cam's laying around. I'll take a look to see if I can find an A cam. I do have an aggressive non turbo reground cam but I dont think that will help me much since the turbo is sized so small.

 

@ letitsnow - Good to know about the other plugs, next time im due for a replacement I'll be sure to look into those. The car feels great, pulls very nicely with the current setup. Plenty of power through the full RPM range. Unfortunately I've never been in a low CR 280zx yet to compare the difference.

 

@ roger280zx - I'm thinking I'll try to calculate the intercooler efficiency with the setup as is. Then later I'll add some ducting and compare the differences. I don't think I'll change the angle of the intercooler this summer, if I do it might be more of a fall/winter project. (summer is a busy time for me). The current setup in the car feels great so I'm not in too much of a panic to change anything.

 

@ dexter - I'll also close the gap to 25 and see how that helps.

 

Thanks again all for the input, I'll try to provide some updates to this thread when I can.

[roger280zx]

Current set up in car feels great yet you start a thread about your problems tuning and a lack of being able to run decent timing? If you think it feels great now then wait till you get some air going through your coils and you can slam some timing in the thing... it will blow your mind. Put it off if you want, test all you want, but I'll ask you this... how many racecars do you see with 5 or 6 inches of space between coils? Hell, for that matter how many bone stock street cars do you see with much space at all between the heat exhange elements? You don't because heat exchangers need flow in order to cool, putting gaps in between them hinders that flow Period. There are PLENTY of flat top piston turbo setups out there who do not have the problem you are having. I'm not going to tell you not to change plugs/fool with your gaps, that is just part of tuning. Space creates eddys, eddys reduce flow, reduced flow=less cool air moving accross the coil=hotter, less dense intake charge=less power on less timing.

[letitsnow]

Post your a screenshot of a 3 or 4 gear run datalog with MAT on it, that'll tell us if you're having trouble with the IC cooling.

[Datsun Deron]

@ roger280zx - My apologies if you or anyone thought this was a thread about problems with my tuning or timing, that was not my intention. I made this post entirely just for the record incase anyone else was dreaming of running flat tops and a turbo, perhaps I wasn't clear. From what I've seen there isn't a whole lot of information out there regarding this setup so I thought I'd add my experiences. Most forum threads say to avoid this configuration all together and I'd like to prove that it can be done with decent results. Also with what I've read regarding my combo these results are fairly typical (low boost and retarded timing) so I really wasn't surprised with my findings. That being said I absolutely appreciate everyone's input and will definitely make use of the suggestions that were said. I agree if I can squeeze some more timing out of the thing I'll have even more fun. With the suggestions you've made regarding the intercooler location etc it could save me the hassle and cost of buying a meth kit in the future.

 

Hi all,I thought I'd post my findings on tuning my car for the archives.

 

@ letitsnow - I'll try to do some logging next time I'm out and let you know the outcome. I'll see if I can take off a little early for work tomorrow .

[Datsun Deron]

Well I managed to get out and do some data logging yesterday morning and had some interesting results. I'll have to retract my previous statement about this being an FYI post as I've now got technical questions...

 

I did a 3rd and 4th gear pull to around the 5300-5500 mark.

-The lowest IAT that MS saw during the drive was 58 which is consistent with the weather network.

-At the beginning of the pull @1800 rpm my IAT's were 64.5 (first screen shot)

-At the end of the 3rd gear pull my IATS were at 87 degrees (second screen shot)

-From here on out the IATS just keep climbing and climbing

-At the end of my 4th gear pull my IATS were at 102 (last screen shot)

-I wasn't able to get into 5th since the speeds were getting up there.

 

 

I was very surprised to see the IAT's continue to climb until I let off the throttle. In my mind I thought it would level off somewhere but there was no sign of that. I'm just wondering if the readings from this sensor are actually accurate. The sensor has a potential of getting heat soaked from external sources, radiator etc. That being said I can't see it getting heat soaked that fast when the car is moving I've just seen heat soaking at idle. My turbo has a heat blanket and my manifold is wrapped as well. The only potential candidate I could see would be the radiator. Also when I let off the throttle between gear changes the IAT temps did level off. So that must be an indication that it is accurate?

 

Have others seen similar results where the IATs continue to climb on runs with multiple gear changes?

 

As far as I can tell there are two major issues that need to be addressed. The air filter is pulling in hot air behind the radiator. (im not running a shroud anymore like the picture below since I'm running a pusher style fan now). And the poor placement of the intercooler with no ducting. I also need to change the bins in my timing and VE table as im getting into the 180s for MAP at times.

 

The picture below shows where my IAT sensor is (it's on the bottom of the pipe) right before the throttle body.

 

It looks like I've got some changes to make and more data logging to do.

Edited July 7, 2012 by Datsun Deron

[letitsnow]

The temperature continuing to rise is completely normal. Intercoolers are in effect a thermal reservoir, the cooling capacity of the atmospheric air flowing through them isn't on the same level as the heating capability of the turbo. There is more heat going in(turbo) than coming out(atmosphere), so the aluminum heats up, raising the intake temp. Air DOES still cool the IC while on boost, just not anywhere near as much as the turbo heats it. This will hit a steady state at some point, but it is higher than what we want. After you get off the throttle and the turbo is no longer heating the air, then it's relatively easy for the atmospheric air to cool the IC down to ambient.

 

The vertical flow IC's are great for engine airflow, but they sacrifice some cooling capability.

 

My car, on the dyno(not anywhere near the airflow of going down the road), MAT started at 75F and ended at 110F. I see much less of a rise while actually driving.

Edited July 7, 2012 by letitsnow

[dexter72]

Of course when you have time, try the suggestions mentioned. It is mentioned in the archives that an n/a cam works really well with the flat top engine and gives the engine more rpm. I upgraded to a larger T3/T4 turbo, That was the most bang for the buck I made. Megasquirt which you have, was my next best upgrade. My timing numbers are close to yours but with a larger turbo running at 15 psi, so keep that in mind. If your looking for more power it's time to upgrade.

 

I started my entire setup with just adding a stock turbo to my n/a engine and running it on stock electronics. That was fun but I kept upgrading when I had time, the difference between then and now is like night and day.

[Six_Shooter]

Well I managed to get out and do some data logging yesterday morning and had some interesting results. I'll have to retract my previous statement about this being an FYI post as I've now got technical questions...

 

I did a 3rd and 4th gear pull to around the 5300-5500 mark.

-The lowest IAT that MS saw during the drive was 58 which is consistent with the weather network.

-At the beginning of the pull @1800 rpm my IAT's were 64.5 (first screen shot)

-At the end of the 3rd gear pull my IATS were at 87 degrees (second screen shot)

-From here on out the IATS just keep climbing and climbing

-At the end of my 4th gear pull my IATS were at 102 (last screen shot)

-I wasn't able to get into 5th since the speeds were getting up there.

 

 

I was very surprised to see the IAT's continue to climb until I let off the throttle. In my mind I thought it would level off somewhere but there was no sign of that. I'm just wondering if the readings from this sensor are actually accurate. The sensor has a potential of getting heat soaked from external sources, radiator etc. That being said I can't see it getting heat soaked that fast when the car is moving I've just seen heat soaking at idle. My turbo has a heat blanket and my manifold is wrapped as well. The only potential candidate I could see would be the radiator. Also when I let off the throttle between gear changes the IAT temps did level off. So that must be an indication that it is accurate?

 

Have others seen similar results where the IATs continue to climb on runs with multiple gear changes?

 

As far as I can tell there are two major issues that need to be addressed. The air filter is pulling in hot air behind the radiator. (im not running a shroud anymore like the picture below since I'm running a pusher style fan now). And the poor placement of the intercooler with no ducting. I also need to change the bins in my timing and VE table as im getting into the 180s for MAP at times.

 

The picture below shows where my IAT sensor is (it's on the bottom of the pipe) right before the throttle body.

 

It looks like I've got some changes to make and more data logging to do.

 

What kind of IAT sensor are you using? The closed GM style sensors had this problem, since the intake it was threaded into would transfer the heat to the outside of the sensor, creating false readings. Usually the rate of change seems to be slower than what your logs show though. Open element sensors are much better at detecting actual intake air temp, since the element itself is open to the air.

 

 

The temperature continuing to rise is completely normal. Intercoolers are in effect a thermal reservoir, the cooling capacity of the atmospheric air flowing through them isn't on the same level as the heating capability of the turbo. There is more heat going in(turbo) than coming out(atmosphere), so the aluminum heats up, raising the intake temp. Air DOES still cool the IC while on boost, just not anywhere near as much as the turbo heats it. This will hit a steady state at some point, but it is higher than what we want. After you get off the throttle and the turbo is no longer heating the air, then it's relatively easy for the atmospheric air to cool the IC down to ambient.

 

The vertical flow IC's are great for engine airflow, but they sacrifice some cooling capability.

 

My car, on the dyno(not anywhere near the airflow of going down the road), MAT started at 75F and ended at 110F. I see much less of a rise while actually driving.

 

I think this depends greatly on the Intercooler system. I know in my case, the intake temps will drop from steady state cruise when getting into boost, and then usually stay there, maybe raise a few degrees over a run.

[letitsnow]

Do you have a real big IC? You also have a bigger(more efficient) turbo IIRC. From previous logs, the t3 at ~10psi is putting out 200-240* temps pre intercooler, mine at 17-19(falls off hard after peak tq) is probably over 300.

 

All IC's will do this to an extent, but if you can shed heat as fast as you put it in(huge IC and efficient turbo/lower boost/meth), the IC temp won't change. Heat in vs heat out is the key thing here.

Edited July 7, 2012 by letitsnow

[Six_Shooter]

Yes, I have Borg Warner turbo from a 6.5L diesel installed currently.

 

Before I installed the IC, I noticed intake temps would peak out at about 180* F @ 9 PSIG (I think I saw 190* F once!). I'd let off at that point, that was quite warm enough for me. After installing the IC, as long as I don't let the IC get heat soaked, the intake temps will stay below 100* F, usually within a few degrees of ambient temps.

 

My IC is home made from two Ford Turbo Coupe cores, and custom tanks.

Edited July 7, 2012 by Six_Shooter

[Datsun Deron]

@ letitsnow - Thanks for the info thats very interesting and a relief. I'd be curious to see now what happens on a 1st to 4th run.

 

@ dexter72 - Good to know I will install an NA cam as soon as I can. I can really feel the power start to drop off around the 5000-5500 mark so that should help. I'll get to a larger turbo one of these days .

 

@ six_ shooter - I'm am using the typical GM sensor. Great info on your setup and regarding not running an intercooler. 180 and 190 is getting up there wow.

[aarang]

Another thing to consider is I had more detonation problems when I was running a 180deg thermostat as apposed to a 160deg. What temp thermo are you running? I finally ditched the stock radiator and put in a aluminum radiator with twin Spal fans and a shroud. Just doing that also helped. I used to have wide temp swings with the stock radiator. My temps rarely get hot enough now to even turn the fans on @176 deg in 85+ deg weather.

[Six_Shooter]

@ six_ shooter - I'm am using the typical GM sensor. Great info on your setup and regarding not running an intercooler. 180 and 190 is getting up there wow.

 

Please define "Typical GM sensor" GM uses both the open element and the closed element MAT sensors, so which are you using?

[Pyro]

Add some meth/water injection and then more ignition timing would be possible.

[rayaapp2]

Let me post my un-educated results with the same setup.

P90 head

Flat top F54 motor with 180K miles

MLS head gasket .9mm

No intercooler!

23* BTDC

RCengineering 500cc injectors

248LPH fuel pump

fuel pressure set at 55psi/70psi

JSK fuel rail barbed

NGK copper core heat range 8(2 steps colder) gapped at .032"-.035"

'A' cam

And a worked over VAFM.

@16lbs of boost I had no detectable detonation audibly or at the stock det sensor(which I feel is a low res sensor anyway).

The car was driven for 3 years like this and hard.

I went to 18PSI! and the engines life ended a few weeks later after a failure of the 81 turbo CAS. It decided to go haywire(on heat soak) and shoot my timing all over the place. Before I lost the CAS I discovered I needed more retard than the ECCS system could give me at 21*. After a taredown I found stress cracks on the #6 pistons skirts and I lost the ring lands on #6... Only.

 

This was a back yard job though. Everything cost me $1000 in total to build that car. I just wanted to see how far I could go. I found the limit with my equipment. Mind you I did have a nice array of tools at my disposal for tuning it. Definitely not the tools you will find in any garage mechanics hands.

To this day I toss those 81 turbo CAS's in the dumpster. Heat soaking them is their downfall and their location is just asking for that to happen.

 

It was a fun car. I have not had too many cars I could abuse like that one. Try fith gear drop launches. 195/50R15 tires burn right off! With the tune and archaic turbo the boost came on like a light switch around 2800rpm.

 

I cannot tell you what the differences are between the 2 builds here claiming 14ish BTDC base timings and mine, but Id say we did something different.

 

With this setup I found that over-fueling was the answer to any detonation. Pig rich AFR's. I doubt it was a long term 100K mile setup, but I built the car like a track car and expected to go through a motor or 2.