recommended PSI for stock block/head pushed by 50trim

[Beanokid69]

I want to know what I can safely boost at with a stock block and head and a pte 50. 91oct+75/25 meth injection m5 nozzle

you can better see my mod list from my profile

 

[winterftbl]

It all depends on tune. Most people run low 20's boost, so with meth injection you should be able to go with 30 + but again its all about tuning.

 

[eclipsegsx1736]

You're asking 2 different questions at once.

How high can you boost with your stock block/head? If you aren't getting knock, you could probably boost as high as 27 psi without any problems, at least short-term. I boosted around 26 psi for almost a year on my bone stock 7 bolt (even stock HG and studs) with no problems. I did blow a hole in the block but only because the WG came disconnected and the boost gauge pegged at over 40 psi . Just watch for knock carefully, keep it on the rich side and run enough timing to keep heat down. You can boost quite a bit higher than most people will recommend on a stock block, but you just have to know what you're doing and back off if you get any serious knock, and immediately retune to eliminate the knock.

How high can you boost on 91 + your injection? Impossible to say without trying. You have DSMlink so you should easily be able to find your boost limit on 91. Put timing to stock and put a conservative rich tune on, and start turning up the boost until you get knock. Then back off a little and tune from there. M5 nozzle is pretty small FYI, and running pure meth with a bigger nozzle (maybe M7 or M10 nozzle) will allow you to run MUCh more boost. If you're injecting 75% water and 25% meth you aren't getting that much of a benefit from injection. I run around 29 psi on a GT30R with pretty high timing and no knock on only 91 octane, but I'm using pure meth and 2 nozzles, an M15 and an M7 together..

 

[1gDSM4g63]

Meth injector will only raise the boost 3-4 lbs. However, I wouldn't go too far with a stock block and no internals what so ever on a car that's 15 yrs old. It could give out at anytime so don't try to make your car something its not.

 

[dsm-onster]

Since you have injection and dsmlink, you're the only one who can find out what your setup will do. We're all bench racing here. From my experience. . .

I was able to run 30+ psi w/ pump gas and a conservative tune w/ my 60-1 and a fmic using pure h2o. You'll need much more nozzle for a 50/50 meth injection mix or a MUCH, MUCH bigger nozzle (set of nozzles) for meth injection. I got similar results w/ running properly sized sets of nozzles for water or meth or a mix. W/ the pure met I was able to bump up my time a bit more, which is always good.A rule of thumb is to look at the hp level you want and fid the corresponding lb/min airflow. Then based on the a/f ration you feel comfortable w/, calculate the fuel flow pure water injection works best w/ a nozzle that is 15-20% fuel flow. pure meth works best w/ a nozzle at around 45-50% fuel flow. A mix lies somewhere in between. . .

I got away w/ 26 psi on the stock head gasket and head bolts. It really doesn't matter which head gasket you use if you're running oem head bolts, especially 7-bolt head bolts. Because knock w/ oem bolts at this level lifts the head, stretching the bolts and the combustion blows around the head gasket. So it doesn't matter if its MLS or made of diamond, unless you run arp head studs. I've not seen anyone get away w/ much more tha 25-26 psi on a stock long block (head blots and composite gasket). Considering what the stock long block will flow, any more power (cylinder pressure) and the knock becomes too strong and the setup becomes too finicky to tune (unless you run race fuel or injection).

 

[eclipsegsx1736]

Dsm-onster: what size nozzles have you run (m10, etc.) and at what pressure on straight meth and high boost? (28+) Just trying to get a ballpark figure on the size.

Also what AFR do you personally shoot for when injecting straight meth at a high % of total fuel flow?

 

[Beanokid69]

it says in my profile that i have apr headstuds

 

[Black_Bullet]

Basically... If your not worried about the longevity of your motor or other related parts ( drivetrain etc. ) then run as much boost as you can succesfully tune for without knock...

 

[dsm-onster]

Dsm-onster: what size nozzles have you run (m10, etc.) and at what pressure on straight meth and high boost? (28+) Just trying to get a ballpark figure on the size.

Also what AFR do you personally shoot for when injecting straight meth at a high % of total fuel flow?

Two 11 gph at 100psi nozzles ( I have an adjustable pressure shurflo pump). I recorded 52 lbs/min and the turbo blew shortly after. So I cannot say that it was a lucky pull or if it could have been consistantly done. . . 31 psi, stock headports/intake manifold. Fp2X cams. 60-1 in an E cover w/ a t3stage 3 turbine in a BEP turbine housing. I ran 26-28 psi daily. I could never get my boost to be consistant due to the internal gate .

I find that running methenol pumps up the lb/min number a bit. Likely because of the supercooling effect of the alcohol. Since it atomizes easer, and accepts heat quicker, it literally sucks the heat out of the aircharge in an instant. Water takes more time and an earlier engagement point.

I ran ONE 11 gph nozzle for a bit w/ straight meth. Though the air is cooler, I got more knock than running straight h2o w/ the same nozzle. I feel this is because there was enough meth to cool the aircharge better than a FMIC, BUT the increase in oxygen in the combustion chamber (which we all want) meant that compression/combustion heat increases leading to preignition. There was not enough meth in the chamber to increase the octane of the fuel mix enough to slow the burn. However, the straight water cooled in the CHAMBER instantly where it didn't in the intake stream. So I looked into what GN guys run for meth injection and they run MUCH more nozzle. I found that they were injecting 50% of total fuel flow for meth. I added another 11gph and my knock went away, I dialed my fuel back a bit and wala!

I shoot for 10.5-11.0:1 a/f ratio for WATER injection. Probably a little conservative. But I havn't melted a piston either. I run a very little more aggresive timing curve over stock. no more than a degree or 2 at any point. W/ most of the timing changes made up top of course.

I do differently w/ meth or meth mix. I look at lambda not a/f ratio on my lm-1 when tuning. The lambda number is much better to use when you're transitioning fuels (gas/meth mix). A wideband measures labda and calculates A/F ratio. Fortunately my lm-1 displays both and I can tell it to calculate a/f ratio for different fuels. Since Lambda is the ratio of actual Air Fuel Ratio to Stoichiometric Air Fuel Ratio, it provides better way to express leanness conditions when you have more than one fuel w/ different stoich numbers. A good real-world explanation of this is to look at the E-85 guys. When driving purely on E85 you can blend it with up to 25% gasoline in case you want to raise the AFR number used to produce max. power. In that case you can raise the boost even further since the volume of fuel needed to reach the desired lambda is decreased because the stoich a/f ratio for gasoline is higher than stoich for E-85 and also meth.

I look for .75 lambda. This comes out to 11:1 if you were to run straight gasoline. Since, about 1/3 of the fuel injected into the combustion is methenol, for the lambda number to read the same, the fuel mix has to be much richer. But still, the mix is at the proper level for good combustion. Since a stoich mixture for methenol is around 6.4:1, for lambda to be the same .75, then the true air to fuel(meth & gas) ratio is between 6.4:1 and 14.7:1. I don't bother telling the lm-1 to calculate a/f ratio for a different fuel because there is no setting for a mix. I don't know the actual a/f number nor do I care, because I have what I really want: the oxygen content of the exhaust. . . Because Lambda = %O2_of_air / (%O2_of_air - %O2_of_exhaust).

This is why so many guys have run methenol and popped their engine. They introduce just enough methenol to make a highly volatile mixture. The amount of meth mixed w/ the air(oxygen) present equals a leaner than stoich (for meth) mixture. The gasoline is then the material preventing detonation! As it accepts a higher ratio to be stoich. If you're injecting just a little meth-- 25% of fuel flow or less-- then there's not enough to worry about this issue and your setup is only using the aircharge cooling poroperties of the meth. So, you just have a great intercooler. But if you want meth to do what it CAN do in the combustion chamber you need lots more and tune to what a wideband really sees which is lambda.

So in all my rambling, I used 2 m11s (your turbo has the potential to flow what mine did) and tuned fuel based on lambda.

 

[dsm-onster]

it says in my profile that i have apr headstuds

I didn't read your profile like I should have. I ASSumed that a stock head means stock head bolts. . . You're good for 30 psi if you get NO knock. Considering that's what many can do w/ a good tune. But again it's based on what your set up puts out. Your engine's cylinder pressures can be vastly different from anothers w/ similar mods.