Ok, so high mile bone stock B16 with T3/T4 50 trim .63hot side running 10 psi. Car is having an issue that we thought was the turbo and small exhaust on the first dyno tune. The car would come up on boost and at 52-5500rpm it would peak and then hold power and then drop like a rock. Vtec changes and you can hear the transition on the dyno and also see a spike in boost pressure very quickly until wastegate catches up. Car made 200 on DynoDynamics at 10psi...Ugh~

Same car, different dyno, different day. Added 2.5" downpipe, changed turbine housing ( old housing turbine was hitting the inside) and fixed a few leaks. Changed the Map sensor to 2.5 bar and turned it up to 12psi. Street tuned it and then took to dyno. Car made 210hp/179tq on dynojet at 3.1psi with a spike at 5200 to 6psi for a split second then the problem is more obvious. Car flat lines after VTEC engages and the studders alot and then falls off. 11.5-11.8AFR, Max timing at 8000@12psi was like 17*. Went up and down with timing +/- 2* with no effect on high cam. Only mods to the calibration that would have any effect was +/- fuel. Car is sync'd with dizzy.

Could Vtec be dropping out after engagement? Does car need more timing just to get it settle out? I didnt want to try it when it didnt make a change in power output.

I dont have graphs in hand yet. But it resembles every stock B16 10psi all the way to 5500 ( roughly 200whp) and then it slides off horrible on HP like it was the torque line with a bad exhaust system.

 

Can someone help with this problem. Also, I have the dyno graph for the 3psi run that spikes to 6psi at Vtec and then settles back to 3 to redline. Can someone help post that as well? If not I will try to post it later.

 

post your dyno graph, your fuel/ignition map

we need more details to help you.

 

maybe the vtec rocker assymbly isnt locking it on all valves maybe looses oil presure so vtec comes off without u knowing

 

Thanks for the help on this, however, I thought the same and went back to find I had over75psi with Vtec activated and that the rockers were all in good shape. I sent the car back to the owner and he found some items that were electrical related and distributor related. I'll update with the findings.

 

stock Cam? Post ur dyno sheet

 

Boost set to 10psi, Vtec set to 5600 and yes I know it has a bad rich spot at crossover. That was the least of my worries. The wideband for dyno was off by roughly 2 points due to the sniffer at back and big leak in muffler. Mine was in DP reading 11.2-11.8 through all the popping. If you have any other ideas, I welcome your suggestions. For reference, the first couple pulls hit biist cut (13psi) at roughly 5600 and the car consistantly made 195-198whp before Vtec and 210whp after tuning that portion a bit more just like it should with 12.0AFR and running 16* right at crossover.

 

When you hit Vtec at 5600 did it spit and sputter or just not engage?

 

Spit and sputtered just like the graph suggests. It did engage and stayed engaged. 10% fuel up and down improved but not very much at all. 2 degrees plus and minus did not do anything. The owner found some electrical items and a loose connection inside the dizzy. I am hoping that was it the whole time as yesterday before he found these, the car failed to crank at all.

 

looking at your graph it looks like its ignitiona related. Check the cap, rotor and internal wires.

Also you are only running 3 psi of boost ===>Gay lol???? and your r running only 16* timing? i would be running at least 22-24* on 3 psi.

 

Graph was of 10psi run that had roughly 18*. my original statment was regarding 12psi with 17* ignition. The 3psi runs were to establish wastegate pressure runs and also to eliminate the boost contrller issue I was having and then start tuning.

K20- owner of car found some loose components inside the dizzy so you correct. Gap is fine and the car has smoothed out since he found that. I have not had a chance to continue tuning on it since he found those items. I should have it back over the weekend and post back with around 280-300whp once this gets remedied. Thanks for your suggestions.

 

also, how is the dump tube routed? that could be ur problem too if the dump is exiting close to the turbo. i was tuning a GSR last night making ~310whp on 12psi. the dumptube was not extending under the car. i extended the dump and then next pas car made 349whp.

 

post your bin.

 

K20, youre all over it. Dump was open and right next to the inlet of turbo, however, we were thinking that it would still work out as the owner didnt have the materials to finish the dump and the one on my car was too short to get it past the turbo. We placed a fan near the turbo while at the dyno to help mitigate the problem, I guess it didnt work out. He just finished the dump and all the other problems I pointed out, so we will see how round 2 goes. Thanks for all the responses.

 

agreed! sounds like you have a timing issue.

 

i guarantee you will see a BIG improvement with the dumptube added (make sure it routed under the oil pan. dumping right at the turbo inlet even with a fan pointed at the turbo inlet is gonna rob serious HP)

Post up the results when its all done!

 

you can see right where the wastegate opens up ~5.5K the graph starts getting funky. typical signs of exhaust gases from the wastegate getting sucked back into the turbo

 

Funny thing was I never caught that. I suck! I was having a horrible day with no datalogging and trying to use the dyno for all the info. It was going sort of ok, till we hit that point. I havent gotten back on it yet, its been raining, so I will post up shortly when he brings it back to finish it up on the street before we take it back to dyno for the Vtec pulls. I just want to review my map once more before getting on the rollers. I am sure its fine but I want to rule everything out.