Boost safety and RPM's
 

I had my car tuned to 403/398 at 10psi on E85 using the PL kit with the standard GT35r.

Problem is that the tune is set up for "Safety" and the boost doesnt really ramp in hard untill 4K rpms. My tuner said he set it up this way for safety cuz if you start pushing that much boost earlier in the rpm range that you are in the "danger zone".

I am wondering if this is true at the power level Im at. It used to come in at about 3.2K but I was pushing a little less power. I would like it to come in faster but I also do not want to risk a blown engine. Is there truth behind this method? Can i still have it ramp in faster and be just fine?

You can overshoot if boost isn't dialed in correctly - all depends on the tuning. If a tuner is prepared to spend the time, he should be able to pull boost in quicker and not compromise safety at all. Most tuners get a flat fee for tuning, so its in their interest to just get it done as fast as possible. Others do a great job and develop a great reputation.

Midrange is when you produce the most torque so higher boost in the lower rpms will put a significant more amount of load on rods than high boost in higher rpms.

You still should be able to tune it to get boost down low safely though.

So to that account...Wouldnt twins put major stress on everything beings they start hitting boost before the 2k range and can hit max by 3500?

For instance fast intentions new twin kit for the 370 is getting 2psi at 1800 and 8psi by 3300 and making 400ft/lbs by 3300.

As long as you don't have too much tq I don't see how it matters where it kicks in. It's not too often you'll actually be hitting full boost at low RPMs anywhere but a dyno or a freeway pull starting in the wrong gear... I have 300wtq at 2krpm on a dyno and full spool on the street by 3krpm for several years without issues... it's all in the tune.

the entire point of E85 is to bring on boost earlier, due to increased exhaust volume. You can make those 10pai numbers on pump gas with the same margin of safety, so you tuner is completely screwing you out of the sole reason of using E85 on a stock block.

Just tell your tuner you will only boost going down hill ;)

Damn, now i do feel left wanting more. Wonder if we can street tune this for quicker spool up lower in the range....?

+1. If the torque produced is still safe for the engine then it will be fine.

But yes, boosting thus higher toque in low rpms does load the engine. Same as running a really low gear ratio (higher gear selection).

So when I had my Stillen SC i had 8lbs at 1800 and my torque line went straight up to peak at 3000k. How can that be safe? Is it just becuase your not moving that much air with the SC?

How much torque was it? stillen at 8psi doesn't produce that much power. 300tq at 3k isn't going to be unsafe but 400tq is probably going to be pushing it.

Why are you trying to boost at 1800 rpms? I don't even cruise on the highway that low. I've never understood the fascination with getting boost 2000 rpms before you would ever really use it. Even then I've never raced at 3k rpms. 6 gears in that transmission to allow easy gear selection for proper power. :)

Im not trying to boost at 1800. I was just making a point that it has already been there. But yeah I was making considerable less peak power.

Well its not torque im directly after but its correlated to turbo lag. I cruise around at 2k to 2.5k. When i want to go and mash the throttle it takes untill 4k to get the power to kick in. Im just not used to this and would rather have it come in earlier.

Looking at other dyno graphs such as twins or the bp setup, it comes on much earlier. The guy who just posted up his bp dyno has about 310ft/lbs at 3k and is running pump gas with no return system. Were hitting the same peak numbers but he is getting there much earlier.

Im at 175ft/lbs at 3k.

Im just wondering why I went with 1000cc injectors, frs, billet rails, bigger feed line and E85. Kind of did it to have quicker spool more safely. But right now its looking like that would have been possible on just 91.

ya, you should be able to pull in the boost sooner. 300 at 3k isn't really much of a danger to the engine.

If you can get ahold of a dyno with boost plot on it we can see what the tuner did. Maybe he set it to ease in boost with the controller. Doesn't really make it any safer that way with the number you are at though.

what did he use to tune it?

Funny thing is i asked for a boost plot and they said they would get it to me. Then when my car got lowered off the dynojet they handed me the sheet and no boost or afr plot.

Im using a haltech. I think he just used the haltechs boost readout and my defi in cabin.

Can you take a log with rpm, boost, boost controller duty cycle and target? If you don't mind send me your map and I'll take a little look at it. I won't be finished at the office until about 7 but I have a little bit of free time here in a little while.

jeffbinder@gmail.com

I am very unfamiliar with the haltech software. The only thing ive done with it was import and upload a base map that a bud of mine sent me. How would I go about exporting the map? I am looking at my old maps right now but for some weird reason they all show todays date and state it as date modified. Ill have to go hook my laptop back up to the unit and try to figure it out. My tuner used his own laptop to tune with so its not on mine right now.

So once hooked up will it upload the map into the haltech software? THen go nissan folder and Z33?

send me an email. I can walk you through it easier that way. Have no fear, you can download the current map on the car to your computer with ease.

You have a gmail my friend....

If you wanna make more boost, its very easy with the haltech

Just go to your open loop base duty table.

copy whatever values you have at 4000 rpms into your 2000 and 3000 rpm boxes.

go for a spin :)

I looked at the map. Problem with that theory Rich is the tuner didn't use the haltech boost controller.