I dynoed my car last fall, before and about a month after I installed a set of Strup headers. The headers gave me a nice gain and my best run was almost 248 hp. It was around 70 degress, with about 37% humidity during that run. BTW, this is on a dynojet dyno.

Since then I installed a 5/16th spacer and Borla TD exhaust. I decided to go back to the dyno to see how much power I now had and to make sure I wasn't running too lean. I used the same 93 octane gas and Mobil 1 5w30 that I did for my other dyno runs.

The good news is I'm not lean. Maybe slightly, around 4000 rpms, I hit 14.1. At redline I was actually running richer than before I installed the spacer and exhaust. It was around 12.1.

My problem is I put down about 6 less hp tonight than I did before I installed the spacer and exhaust!!! My best sae corrected run was only 242 hp!

I wasn't expecting a huge gain from the spacer and exhaust but I expected some. The spacer has been proving to provide a solid 11-13hp gain. The Borla has shown gains around 8hp. I wasn't expecting to gain the full 19-21 hp but I definately didn't expect to lose any power!!!

Tonight the temperature was around 83 degrees and the humidity was in the mid 70's. Could that have caused my numbers to be that much lower?

 

you need to correct the AF ratio via piggyback or stand alone computer. you will definatly see your gains once you approach the previous stoicheometery. I would try UTEC

 

what was your gain when installing the headers?

 

You definitely need a tune especially after headers. Get a UTEC, The best on the market for the Z. Check My sig!!

 

did/can your shop datalog (via cipher, consult) to see if timing was being pulled during the runs?

i don't see any other way to know for sure what's going on...

 

A 5/16" spacer alone will never give your Z 11whp, please refrain from ricer math as it makes us all look dumb. Now moving on, if your original numbers were also SAE corrected then yes you lost power-or at least didnt gain any, were the original SAE corrected or were they actual? People dont realize how important tuning your ECU/piggyback with mods is, your car now is barely quicker than a stock Z. You just need to tune via your choice. I dont know why you would be richer up top-obviously your ECU is possibly overcorrecting for the mods, but thats weird as 95% of Z's lean out (esp midrange) as they mod and dont actually run richer....

 

there are at least a dozen dynos that show that the spacer WILL make that hp, but ONLY if alone (on an otherwise stock car).

With the other breathing mods, then I agree there is no evidence to support the additional gain of that same hp...

(ricer math, lol)

EDIT: Oops! Corrected by Alberto. This is a revup motor - I take it all back.

 

Wrong in regard to this thread/car. On a REVUP an MREV kit (lower 03' collector machined down+ spacer) will make that power in the midrange, but not PEAK. Only a 5/16" spacer on a standard 287hp motor will NEVER make that power....

 

so the 5/16 spacer is not good on the 287 motor?

 

I think he meant "EVER" not "NEVER". The 287 motor makes the power with the spacer...

(and I stand corrected - edited my post above)

 

i thought i read that the 287 makes power with either the mrev2 or the spacer but when combined you need a tune

 

OT but a 5/16" AAM spacer or 1/2" spacer WILL provide gains, but not 11-13whp on a 287hp Z...I gained 23WHP with almost all bolt-ons AND a tune NA in my car-its not that easy to get power out of these cars if it was we'd all be rocking 300whp NA Z's...

 

I have the 287 hp motor not the rev up.

Alberto, I wasn't using "ricer math". I have read a lot of post that showed about 11hp gains with the 5/16th spacer. Even the test that was done by SportZ magazine verified that the 5/16th spacer gained 11hp. Now I know that since I already gained some power with the headers and popcharger that I wouldn't gain the full 11hp. But I didn't expect to lose any power!

I didn't expect the exhaust to gain much, but again I didn't expect to lose any power either.

My best run before installing the spacer and exhaust was 245.09 hp uncorrected. Last night the best run was 238.80 hp uncorrected. The hp and tq curves are identical just lower. The a/f started off much leaner at over 17.1 at 2000 rpms. But at 2500 it dropped down to 13.5 and went down to below 13.1 until it hit 3500rpms. At that point it rose to 14.1 at 4000rpms and began to drop slowly until 5500 rpms. At 5500 it drops below 13.0 and keeps droping to below 12.0 at redline. The run with just the headers and popcharger didn't didn't drop below 12.5 at redline. It was also richer between 3800 and 5700 rpms, around 13.0to 13.8.

I don't understand why my car is running richer at redline after installing a spacer and exhaust. I thought I would be running leaner. I did lean out slightly in the mid range by @.3 to .6 but I think 14.1 between 3800 and 4400rpms is still safe.

Is there anyway that this could all be because of the very high humidity and temperature last night? It went as high as 85% in the dyno room! If not then what should I do next? Is it possible the spacer is causing me to lose power?

 

maybe a stupid question but what is OT?

 

I believe it means Off Topic.

 

OT=Off Topic

Beeker-IMO it is ricer math when you beleive a magazine who is running a "test" on a product that they advertise-its nothing but a sale ploy. If you believe that then you should believe all the magazine claims for all NA parts and you'd have a 345whp Z-Im telling you Ive dyno'd my car 5 times NA throughout the course of modding its BS. Regarding your car-hotter weather will equal richer A/F's, but the car could be knocking slightly and your ECU will ***** you and pull timing, thus making less power than before. Best thing for you guy to do would be get a piggyback and tune it!

 

I don't believe all the claims that companies and magazines say about horsepower gains. I do think that SportZ magazine seemed to be fair and unbiased for the spacer/plenum test they did. Plus, I have read many posts about people gaining power with a spacer/plenum on 287 hp motors. Even without a tune.

Anyway, I was trying to avoid having to get a piggyback and tune it. That is why I left the stock cats so I wouldn't run lean. I haven't seen enough proof yet that a piggyback can actually prevent the factory ecu from changing things. I know the Utec is suppose to be the cats *** but it is still fairly new and I don't know enough about it to drop a $1,000.00 plus dyno/tune time.

I am thinking I should head back to the dyno on a cool dry night just to see what happens. If I am still making less power then I will remove the spacer and do a few runs without it. If it makes more power without the spacer I am going to be pissed. The amount of time I spent tweaking the strut bar to clear the plenum and not bulge the hood drove me crazy. If I did all that to lose power I will be giving Motordyne a call!

I don't think I will make less power without the spacer installed because I haven't read one post showing a lose of power with a spacer. But who knows at this point.

I was hoping I was done modding this car. I guess I have more work to do...

 

Your being unrealistic in wanting to see gains and not tune it, some can get away with that for a while, others cant. Spend a few hundred on a basic Emanage and tune it, or try Techno's flash send it in with a mods list and dyno with A/F, thats what I did and they tuned my car PERFECT....

 

Alberto, your saying if I send my ECU to technosquare for a reflash I will see the gains I am looking for?

If so should I bother to install a set of hi flow cats or test pipes first? Will they make a noticeable gain along with the proper reflash?

I was thinking about going with a set of hi flow cats instead of testpipes because I don't want it to be too loud. Of course it may be too loud for me with hi flows as well. I think it sounds great now with just the headers and the Borla TD. I've read that it sounds even better with hi flows but I would like to hear it in person before installing a set on my car.

 

got a dyno chart? I would like to see others a/f ratio.